EXHIBIT A

                         FORM OF CLASS A CERTIFICATE

UNLESS THIS  CERTIFICATE IS PRESENTED BY AN AUTHORIZED  REPRESENTATIVE  OF THE
DEPOSITORY  TRUST COMPANY,  A NEW YORK CORPORATION  ("DTC"),  TO ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER,  EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS  REGISTERED  IN THE NAME OF CEDE &amp; CO. OR IN SUCH  OTHER  NAME AS IS
REQUESTED BY AN AUTHORIZED  REPRESENTATIVE  OF DTC (AND ANY PAYMENT IS MADE TO
CEDE  &  CO.  OR  TO  SUCH  OTHER  ENTITY  AS IS  REQUESTED  BY AN  AUTHORIZED
REPRESENTATIVE  OF DTC), ANY TRANSFER,  PLEDGE,  OR OTHER USE HEREOF FOR VALUE
OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL  INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

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Certificate No.                    :     1

Cut-off Date                       :     January 1, 2005

First Distribution Date            :     February 25, 2005

Initial Certificate Balance
of this Certificate
("Denomination")                   :

Initial Certificate Balances
of all Certificates
of this Class                      :

 CUSIP                              :

Pass-Through Rate                  :     Variable

Maturity Date                      :     May 2035

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             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
            Credit Suisse First Boston Mortgage Securities Corp.,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                              Class [__]-A-[__]

      evidencing a percentage  interest in the  distributions  allocable
      to the Certificates of the above-referenced  Class with respect to
      a Trust Fund  consisting  primarily of a pool of  adjustable  rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      Principal in respect of this  Certificate  is  distributable  monthly as
set forth  herein.  Accordingly,  the  Certificate  Balance at any time may be
less than the Certificate  Balance as set forth herein.  This Certificate does
not evidence an  obligation  of, or an interest in, and is not  guaranteed  by
the Depositor,  the Seller,  the Master Servicer,  the Servicers,  the Special
Servicer,  the Trust  Administrator or the Trustee referred to below or any of
their respective  affiliates.  Neither this Certificate nor the Mortgage Loans
are guaranteed or insured by any governmental agency or instrumentality.

      This  certifies  that  CEDE  &amp;  CO.,  is  the  registered  owner
of the Percentage  Interest  evidenced by this Certificate  (obtained by dividing
the denomination of this Certificate by the aggregate of the  denominations of all
Certificates  of the  Class to which  this  Certificate  belongs)  in  certain
monthly  distributions  with respect to a Trust Fund  consisting  primarily of
the  Mortgage  Loans   deposited  by  Credit  Suisse  First  Boston   Mortgage
Securities Corp. (the  "Depositor").  The Trust Fund was created pursuant to a
Pooling and Servicing  Agreement  dated as of the Cut-off Date specified above
(the "Agreement") among Credit Suisse First Boston Mortgage  Securities Corp.,
as depositor,  DLJ Mortgage Capital,  Inc., as seller, Wells Fargo Bank, N.A.,
as trust  administrator,  master  servicer,  servicer and back-up servicer and
HSBC Bank USA, National Association,  as trustee, Wilshire Credit Corporation,
as special servicer, Select Portfolio Servicing,  Inc., as a servicer, and the
other  servicers  that are  signatories  thereto.  To the extent  not  defined
herein,  the capitalized  terms used herein have the meanings  assigned in the
Agreement.  This  Certificate  is issued  under and is  subject  to the terms,
provisions and conditions of the Agreement,  to which  Agreement the Holder of
this Certificate by virtue of the acceptance  hereof assents and by which such
Holder is bound.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

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      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  ___________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By_______________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                              Class [__]-A-[___]

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed  Pass-Through Certificates,  Series 2005-1, of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

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                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

_______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to
______________________________________________________________________________,
for the account of ___________________________________________________________,
_______________________________________________________________________________
account number _______________, or, if mailed by check, to ____________________
_______________________________________________________________________________
_______________________________________________________________________________
Applicable statements should be mailed to _____________________________________
_______________________________________________________________________________
_______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                                                       EXHIBIT B

                        FORM OF CLASS 5-M CERTIFICATE

UNLESS THIS  CERTIFICATE IS PRESENTED BY AN AUTHORIZED  REPRESENTATIVE  OF THE
DEPOSITORY  TRUST COMPANY,  A NEW YORK CORPORATION  ("DTC"),  TO ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER,  EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS  REGISTERED  IN THE NAME OF CEDE & CO. OR IN SUCH  OTHER  NAME AS IS
REQUESTED BY AN AUTHORIZED  REPRESENTATIVE  OF DTC (AND ANY PAYMENT IS MADE TO
CEDE  &  CO.  OR  TO  SUCH  OTHER  ENTITY  AS IS  REQUESTED  BY AN  AUTHORIZED
REPRESENTATIVE  OF DTC), ANY TRANSFER,  PLEDGE,  OR OTHER USE HEREOF FOR VALUE
OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL  INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

THIS  CERTIFICATE IS SUBORDINATED IN RIGHT OF PAYMENT TO CERTAIN  CERTIFICATES
AS DESCRIBED IN THE AGREEMENT REFERRED TO HEREIN.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Certificate Balance
of this Certificate
("Denomination")                    :

Initial Certificate Balances
of all Certificates
of this Class                       :

CUSIP                               :

Pass-Through Rate                   :     Variable

Maturity Date                       :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                Class 5-M-[__]

      evidencing a percentage  interest in the  distributions  allocable
      to the Certificates of the above-referenced  Class with respect to
      a Trust Fund  consisting  primarily of a pool of  adjustable  rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      Principal in respect of this  Certificate  is  distributable  monthly as
set forth  herein.  Accordingly,  the  Certificate  Balance at any time may be
less than the Certificate  Balance as set forth herein.  This Certificate does
not evidence an  obligation  of, or an interest in, and is not  guaranteed  by
the Depositor,  the Seller,  the Master Servicer,  the Servicers,  the Special
Servicer,  the Trust  Administrator or the Trustee referred to below or any of
their respective  affiliates.  Neither this Certificate nor the Mortgage Loans
are guaranteed or insured by any governmental agency or instrumentality.

      This  certifies  that  CEDE  &amp;  CO.,  is  the  registered  owner
of the Percentage  Interest  evidenced by this Certificate  (obtained by dividing
the denomination of this Certificate by the aggregate of the  denominations of all
Certificates  of the  Class to which  this  Certificate  belongs)  in  certain
monthly  distributions  with respect to a Trust Fund  consisting  primarily of
the  Mortgage  Loans   deposited  by  Credit  Suisse  First  Boston   Mortgage
Securities Corp. (the  "Depositor").  The Trust Fund was created pursuant to a
Pooling and Servicing  Agreement  dated as of the Cut-off Date specified above
(the "Agreement") among Credit Suisse First Boston Mortgage  Securities Corp.,
as depositor,  DLJ Mortgage Capital,  Inc., as seller, Wells Fargo Bank, N.A.,
as trust  administrator,  master  servicer,  servicer and back-up servicer and
HSBC Bank USA, National Association,  as trustee, Wilshire Credit Corporation,
as special servicer, Select Portfolio Servicing,  Inc., as a servicer, and the
other  servicers  that are  signatories  thereto.  To the extent  not  defined
herein,  the capitalized  terms used herein have the meanings  assigned in the
Agreement.  This  Certificate  is issued  under and is  subject  to the terms,
provisions and conditions of the Agreement,  to which  Agreement the Holder of
this Certificate by virtue of the acceptance  hereof assents and by which such
Holder is bound.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By__________________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                Class 5-M-[__]

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed  Pass-Through Certificates,  Series 2005-1, of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to
______________________________________________________________________________,
______________________________________________________________________________,
for the account of ____________________________________________________________
account number ____________, or, if mailed by check, to________________________
_______________________________________________________________________________
_______________________________________________________________________________
Applicable statements should be mailed to _____________________________________
_______________________________________________________________________________
_______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                  EXHIBIT C

                        FORM OF CLASS C-B CERTIFICATE

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

THIS  CERTIFICATE IS SUBORDINATED IN RIGHT OF PAYMENT TO CERTAIN  CERTIFICATES
AS DESCRIBED IN THE AGREEMENT REFERRED TO HEREIN.

[THIS  CERTIFICATE HAS NOT BEEN  REGISTERED  UNDER THE SECURITIES ACT OF 1933,
AS AMENDED  ("THE ACT").  ANY RESALE OR TRANSFER OF THIS  CERTIFICATE  WITHOUT
REGISTRATION  THEREOF UNDER THE ACT MAY ONLY BE MADE IN A TRANSACTION EXEMPTED
FROM  THE  REGISTRATION  REQUIREMENTS  OF THE ACT AND IN  ACCORDANCE  WITH THE
PROVISIONS OF THE AGREEMENT REFERRED TO HEREIN.]

PURSUANT TO SECTION 6.02(f) OF THE AGREEMENT, AN ERISA-RESTRICTED  CERTIFICATE
OR ANY INTEREST HEREIN MAY NOT BE TRANSFERRED  UNLESS THE TRANSFEREE  DELIVERS
TO THE TRUSTEE (I) A REPRESENTATION  LETTER TO THE EFFECT THAT SUCH TRANSFEREE
IS NOT AN  EMPLOYEE  BENEFIT  PLAN  OR  ARRANGEMENT  SUBJECT  TO THE  EMPLOYEE
RETIREMENT  INCOME SECURITY ACT OF 1974, AS AMENDED  ("ERISA") OR SECTION 4975
OF THE CODE OR A PERSON  USING  THE  ASSETS OF SUCH A PLAN OR  ARRANGEMENT  OR
(II) IF THE  PURCHASER IS AN INSURANCE  COMPANY AND THE  CERTIFICATE  HAS BEEN
THE  SUBJECT  OF  AN  ERISA-QUALIFYING   UNDERWRITING,   A  REPRESENTATION  IN
ACCORDANCE  WITH THE  PROVISIONS OF THE AGREEMENT  REFERRED TO HEREIN OR (III)
AN OPINION  OF COUNSEL IN  ACCORDANCE  WITH THE  PROVISIONS  OF THE  AGREEMENT
REFERRED  TO  HEREIN.  IN THE EVENT  THE  REPRESENTATIONS  REFERRED  TO IN THE
PRECEDING SENTENCE ARE NOT FURNISHED,  SUCH REPRESENTATION  SHALL BE DEEMED TO
HAVE  BEEN  MADE  TO  THE  TRUSTEE  BY THE  TRANSFEREE'S  ACCEPTANCE  OF  THIS
CERTIFICATE,  OR BY ANY  BENEFICIAL  OWNER WHO  PURCHASES  AN INTEREST IN THIS
CERTIFICATE  IN  BOOK-ENTRY  FORM.  IN  THE  EVENT  THAT A  REPRESENTATION  IS
VIOLATED,   OR  ANY  ATTEMPT  TO  TRANSFER  THIS  CERTIFICATE  TO  A  PLAN  OR
ARRANGEMENT  OR PERSON  USING A PLAN'S OR  ARRANGEMENT'S  ASSETS IS  ATTEMPTED
WITHOUT  THE  DELIVERY  TO THE  TRUSTEE OF THE  OPINION  OF COUNSEL  DESCRIBED
ABOVE,  THE ATTEMPTED  TRANSFER OR  ACQUISITION OF THIS  CERTIFICATE  SHALL BE
VOID AND OF NO EFFECT.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Certificate Balance
of this Certificate
("Denomination")                   :

Initial Certificate Balances
of all Certificates
of this Class                      :

Percentage Interest                :     100%

CUSIP                              :

Pass-Through Rate                  :     Variable

Maturity Date                      :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                Class C-B-[__]

      evidencing a percentage  interest in the  distributions  allocable
      to the Certificates of the above-referenced  Class with respect to
      a Trust Fund  consisting  primarily of a pool of  adjustable  rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      This  Certificate does not evidence an obligation of, or an interest in,
and is not guaranteed by the Depositor,  the Seller, the Master Servicer,  the
Servicers,  the  Special  Servicer,  the  Trustee  or the Trust  Administrator
referred  to  below  or any  of  their  respective  affiliates.  Neither  this
Certificate   nor  the  Mortgage  Loans  are  guaranteed  or  insured  by  any
governmental agency or instrumentality.

      This certifies that [_____________________________________________],  is
the registered owner of the Percentage  Interest evidenced by this Certificate
(obtained by dividing the  denomination  of this  Certificate by the aggregate
of  the  denominations  of  all  Certificates  of  the  Class  to  which  this
Certificate belongs) in certain monthly  distributions with respect to a Trust
Fund  consisting  primarily of the Mortgage  Loans  deposited by Credit Suisse
First Boston Mortgage  Securities Corp. (the "Depositor").  The Trust Fund was
created pursuant to a Pooling and Servicing  Agreement dated as of the Cut-off
Date  specified  above (the  "Agreement")  among  Credit  Suisse  First Boston
Mortgage  Securities  Corp.,  as  depositor,  DLJ Mortgage  Capital,  Inc., as
seller,  Wells Fargo Bank,  N.A.,  as trust  administrator,  master  servicer,
servicer and back-up  servicer  and HSBC Bank USA,  National  Association,  as
trustee,  Wilshire Credit Corporation,  as special servicer,  Select Portfolio
Servicing,  Inc., as a servicer,  and the other servicers that are signatories
thereto.  To the extent not defined herein,  the capitalized terms used herein
have the  meanings  assigned  in the  Agreement.  This  Certificate  is issued
under  and  is  subject  to  the  terms,  provisions  and  conditions  of  the
Agreement,  to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound.

      [For  C-B-4,  C-B-5 and C-B-6  only] [No  transfer  of this  Certificate
shall  be  made  unless  such  transfer  is  made  pursuant  to  an  effective
registration  statement  under the  Securities  Act and any  applicable  state
securities  laws or is exempt from the  registration  requirements  under said
Act and such  laws.  In the event that a  transfer  is to be made in  reliance
upon an exemption  from the  Securities  Act and such laws, in order to assure
compliance  with the  Securities  Act and  such  laws,  the  Certificateholder
desiring  to effect such  transfer  and such  Certificateholder's  prospective
transferee shall each certify to the Trust  Administrator in writing the facts
surrounding  the transfer and (i) deliver a letter in  substantially  the form
of either  Exhibit L and  either  (A)  Exhibit M 1,  provided  that all of the
Certificates  of  the  Class  shall  be  transferred  to one  investor  or the
Depositor  otherwise  consents  to such  transfer,  or (B) Exhibit M 2 or (ii)
there  shall be  delivered  to the Trust  Administrator  at the expense of the
transferor  an Opinion of Counsel that such  transfer may be made  pursuant to
an exemption  from the  Securities  Act. The Holder hereof  desiring to affect
such transfer  shall,  and does hereby agree to,  indemnify  the Trustee,  the
Trust  Administrator  and the Depositor  against any liability that may result
if the  transfer  is not so  exempt  or is not made in  accordance  with  such
federal and state laws.]

      Pursuant  to  Section 6.02(f)  of  the  Agreement,  no  transfer  of  an
ERISA-Restricted  Certificate  shall be made  unless  the  Trustee  shall have
received  either  (i) a  representation  letter  from the  transferee  of such
ERISA-Restricted  Certificate,   acceptable  to  and  in  form  and  substance
satisfactory  to the Trust  Administrator,  to the effect that such transferee
is not an employee  benefit  plan or  arrangement  subject to  Section 406  of
ERISA or  Section 4975  of the Code,  or a person using the assets of any such
plan or  arrangement  which  representation  letter shall not be an expense of
the Trustee,  the Trust Administrator or the Trust Fund, (ii) if the purchaser
is an  insurance  company and the  ERISA-Restricted  Certificate  has been the
subject  of  an  ERISA-Qualifying  Underwriting,  a  representation  that  the
purchaser is an insurance  company which is purchasing such  Certificates with
funds  contained in an "insurance  company  general  account" (as such term is
defined in  Section V(e)  of  Prohibited  Transaction  Class  Exemption  95-60
("PTCE  95-60"))  and that the purchase  and holding of such  Certificate  are
covered  under  Sections  I and III of PTCE  95-60 or (iii) in the case of any
such  ERISA-Restricted  Certificate  presented for registration in the name of
an employee  benefit  plan  subject to ERISA or  Section 4975  of the Code (or
comparable  provisions of any subsequent  enactments),  or a person using such
plan's or  arrangement's  assets,  an Opinion of Counsel  satisfactory  to the
Trust  Administrator  to the  effect  that the  purchase  or  holding  of such
Certificate will not result in prohibited  transactions  under  Section 406 of
ERISA and/or Section 4975 of the Code and will not subject the Depositor,  the
Trustee,  the Trust  Administrator,  the Master Servicer or any other Servicer
to any  obligation in addition to those  undertaken in this  Agreement,  which
Opinion  of  Counsel  shall not be an  expense  of such  parties  or the Trust
Fund. In the event the  representations  referred to in the preceding sentence
are not furnished,  such  representation  shall be deemed to have been made to
the trustee by the transferee's acceptance of an ERISA-Restricted  Certificate
or by any  beneficial  owner who purchases an interest in this  certificate in
book-entry  form.  In the event  that a  representation  is  violated,  or any
attempt to transfer an  ERISA-Restricted  Certificate to a plan or arrangement
or person  using a plan's or  arrangement's  assets is  attempted  without the
delivery  to the  Trustee  of the  Opinion  of Counsel  described  above,  the
attempted  transfer or acquisition of this certificate shall be void and of no
effect.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By ________________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                Class C-B-[__]

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed  Pass-Through Certificates,  Series 2005-1, of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to____________________________________________________________
_____________________________________________________________________________,
for the account of __________________________________________________________,
account number __________________, or, if mailed by check, to ________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to ____________________________________
______________________________________________________________________________
______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                 EXHIBIT D-1

                         FORM OF CLASS AR CERTIFICATE

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP OF "RESIDUAL  INTERESTS" ISSUED BY "REAL ESTATE MORTGAGE  INVESTMENT
CONDUITS,"  AS THOSE TERMS ARE  DEFINED,  RESPECTIVELY,  IN SECTIONS  860G AND
860D OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

NEITHER THIS  CERTIFICATE  NOR ANY INTEREST  HEREIN MAY BE TRANSFERRED  UNLESS
THE  PROPOSED  TRANSFEREE  DELIVERS  TO THE  TRUST  ADMINISTRATOR  A  TRANSFER
AFFIDAVIT IN  ACCORDANCE  WITH THE  PROVISIONS  OF THE  AGREEMENT  REFERRED TO
HEREIN.

NEITHER THIS  CERTIFICATE  NOR ANY INTEREST  HEREIN MAY BE TRANSFERRED  UNLESS
THE TRANSFEREE  DELIVERS TO THE TRUSTEE A REPRESENTATION  LETTER TO THE EFFECT
THAT SUCH  TRANSFEREE IS NOT AN EMPLOYEE  BENEFIT PLAN OR ARRANGEMENT  SUBJECT
TO THE EMPLOYEE  RETIREMENT  INCOME SECURITY ACT OF 1974, AS AMENDED ("ERISA")
OR  ARRANGEMENT,  OR SECTION  4975 OF THE CODE OR A PERSON USING THE ASSETS OF
SUCH A PLAN OR  ARRANGEMENT.  NOTWITHSTANDING  ANYTHING  ELSE TO THE  CONTRARY
HEREIN,  ANY  PURPORTED  TRANSFER  OF THIS  CERTIFICATE  TO OR ON BEHALF OF AN
EMPLOYEE BENEFIT PLAN OR ARRANGEMENT  SUBJECT TO ERISA OR TO THE CODE SHALL BE
VOID AND OF NO EFFECT.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Certificate Balance
of this Certificate
("Denomination")                    :

Initial Certificate Balances
of all Certificates
of this Class                       :

CUSIP                               :

Pass-Through Rate                   :     Variable

Maturity Date                       :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                   Class AR

      evidencing a percentage  interest in the  distributions  allocable
      to  the  Class  AR  Certificates  with  respect  to a  Trust  Fund
      consisting  primarily of a pool of  adjustable  rate  conventional
      mortgage  loans (the "Mortgage  Loans")  secured by first liens on
      one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      Principal in respect of this  Certificate  is  distributable  monthly as
set forth  herein.  Accordingly,  the  Certificate  Balance at any time may be
less than the Certificate  Balance as set forth herein.  This Certificate does
not evidence an  obligation  of, or an interest in, and is not  guaranteed  by
the Depositor,  the Seller,  the Master Servicer,  the Servicers,  the Special
Servicer,  the Trustee or the Trust Administrator  referred to below or any of
their respective  affiliates.  Neither this Certificate nor the Mortgage Loans
are guaranteed or insured by any governmental agency or instrumentality.

      This  certifies  that Credit Suisse First Boston LLC, is the  registered
owner of the Percentage  Interest  evidenced by this Certificate  (obtained by
dividing  the  denomination  of  this  Certificate  by  the  aggregate  of the
denominations  of all  Certificates  of the  Class to which  this  Certificate
belongs)  in  certain  monthly  distributions  with  respect  to a Trust  Fund
consisting  primarily of the Mortgage  Loans  deposited by Credit Suisse First
Boston  Mortgage  Securities  Corp.  (the  "Depositor").  The  Trust  Fund was
created pursuant to a Pooling and Servicing  Agreement dated as of the Cut-off
Date  specified  above (the  "Agreement")  among  Credit  Suisse  First Boston
Mortgage  Securities  Corp.,  as  depositor,  DLJ Mortgage  Capital,  Inc., as
seller,  Wells Fargo Bank,  N.A.,  as trust  administrator,  master  servicer,
servicer and back-up  servicer  and HSBC Bank USA,  National  Association,  as
trustee,  Wilshire Credit Corporation,  as special servicer,  Select Portfolio
Servicing,  Inc., as a servicer,  and the other servicers that are signatories
thereto.  To the extent not defined herein,  the capitalized terms used herein
have the  meanings  assigned  in the  Agreement.  This  Certificate  is issued
under  and  is  subject  to  the  terms,  provisions  and  conditions  of  the
Agreement,  to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound.

      Any  distribution  of the proceeds of any remaining  assets of the Trust
Fund  will be made  only  upon  presentment  and  surrender  of this  Class AR
Certificate at the Corporate  Trust Office or the office or agency  maintained
by the Trust Administrator in New York, New York.

      Pursuant  to  Section 6.02(f)  of the  Agreement,  no  transfer  of this
Residual  Certificate  shall be made unless the Trustee  shall have received a
representation  letter from the transferee of such Certificate,  acceptable to
and in form and  substance  satisfactory  to the Trust  Administrator,  to the
effect that such  transferee  is not an employee  benefit plan or  arrangement
subject  to  Section 406  of ERISA or  Section 4975  of the Code,  or a person
using the assets of any such plan or arrangement which  representation  letter
shall not be an expense of the Trustee,  the Trust  Administrator or the Trust
Fund. In the event the  representations  referred to in the preceding sentence
are not furnished,  such  representation  shall be deemed to have been made to
the Trustee by the transferee's  acceptance of this Residual Certificate or by
any  beneficial  owner  who  purchases  an  interest  in this  Certificate  in
book-entry  form.  In the event  that a  representation  is  violated,  or any
attempt to transfer  this Residual  Certificate  to a plan or  arrangement  or
person using a plan's or  arrangement's  assets is  attempted,  the  attempted
transfer or acquisition of this Certificate shall be void and of no effect.

      Each Holder of this Class AR  Certificate  will be deemed to have agreed
to be bound by the  restrictions  of the Agreement,  including but not limited
to the  restrictions  that (i) each person  holding or acquiring any Ownership
Interest in this Class AR Certificate must be a Permitted Transferee,  (ii) no
Ownership  Interest in this Class AR Certificate  may be  transferred  without
delivery to the Trust  Administrator  of a transfer  affidavit  of the initial
owner or the  proposed  transferee  in the form  described  in the  Agreement,
(iii) each person  holding or acquiring any  Ownership  Interest in this Class
AR  Certificate  must  agree to require a  transfer  affidavit  from any other
person to whom such  person  attempts to Transfer  its  Ownership  Interest in
this Class AR  Certificate as required  pursuant to the  Agreement,  (iv) each
person   holding  or  acquiring  an  Ownership   Interest  in  this  Class  AR
Certificate must agree not to transfer an Ownership  Interest in this Class AR
Certificate if it has actual  knowledge that the proposed  transferee is not a
Permitted  Transferee  and (v) any  attempted  or  purported  transfer  of any
Ownership  Interest  in  this  Class  AR  Certificate  in  violation  of  such
restrictions  will be absolutely  null and void and will vest no rights in the
purported transferee.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By_____________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                   Class AR

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed Pass-Through Certificates,  Series 2005-1,  of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to ___________________________________________________________
_____________________________________________________________________________,
_____________________________________________________________________________,
for the account of ___________________________________________________________
account number _______________, or, if mailed by check, to____________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to_____________________________________
______________________________________________________________________________
______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                 EXHIBIT D-2

                        FORM OF CLASS AR-L CERTIFICATE

SOLELY FOR U.S.  FEDERAL INCOME TAX PURPOSES,  THIS CERTIFICATE IS A "RESIDUAL
INTEREST" IN A "REAL ESTATE MORTGAGE  INVESTMENT  CONDUIT," AS THOSE TERMS ARE
DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D OF THE INTERNAL REVENUE CODE
OF 1986, AS AMENDED (THE "CODE").

NEITHER THIS  CERTIFICATE  NOR ANY INTEREST  HEREIN MAY BE TRANSFERRED  UNLESS
THE  PROPOSED  TRANSFEREE  DELIVERS  TO THE  TRUST  ADMINISTRATOR  A  TRANSFER
AFFIDAVIT IN  ACCORDANCE  WITH THE  PROVISIONS  OF THE  AGREEMENT  REFERRED TO
HEREIN.

NEITHER THIS  CERTIFICATE  NOR ANY INTEREST  HEREIN MAY BE TRANSFERRED  UNLESS
THE TRANSFEREE  DELIVERS TO THE TRUSTEE A REPRESENTATION  LETTER TO THE EFFECT
THAT SUCH  TRANSFEREE IS NOT AN EMPLOYEE  BENEFIT PLAN OR ARRANGEMENT  SUBJECT
TO SECTION 406 OF THE EMPLOYEE  RETIREMENT  INCOME  SECURITY  ACT OF 1974,  AS
AMENDED  ("ERISA")  OR  ARRANGEMENT,  OR SECTION  4975 OF THE CODE OR A PERSON
USING  THE  ASSETS  OF SUCH A PLAN OR  ARRANGEMENT.  NOTWITHSTANDING  ANYTHING
ELSE TO THE CONTRARY HEREIN,  ANY PURPORTED TRANSFER OF THIS CERTIFICATE TO OR
ON BEHALF OF AN EMPLOYEE  BENEFIT PLAN OR  ARRANGEMENT  SUBJECT TO ERISA OR TO
THE CODE SHALL BE VOID AND OF NO EFFECT.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Certificate Balance
of this Certificate
("Denomination")                    :

Initial Certificate Balances
of all Certificates
of this Class                      :

CUSIP                              :

Pass-Through Rate                  :     Variable

Maturity Date                      :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                  Class AR-L

      evidencing a percentage  interest in the  distributions  allocable
      to the  Class  AR-L  Certificates  with  respect  to a Trust  Fund
      consisting   primarily  of  a  pool  of  fixed  rate  conventional
      mortgage  loans (the "Mortgage  Loans")  secured by first liens on
      one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

            Principal in respect of this Certificate is distributable  monthly
as set forth herein.  Accordingly,  the Certificate Balance at any time may be
less than the Certificate  Balance as set forth herein.  This Certificate does
not evidence an  obligation  of, or an interest in, and is not  guaranteed  by
the Depositor,  the Seller, the Master Servicer,  the Servicer, the Trustee or
the  Trust  Administrator  referred  to  below  or  any  of  their  respective
affiliates.  Neither this  Certificate  nor the Mortgage  Loans are guaranteed
or insured by any governmental agency or instrumentality.

            This certifies that  [__________________________________],  is the
registered  owner of the  Percentage  Interest  evidenced by this  Certificate
(obtained by dividing the  denomination  of this  Certificate by the aggregate
of  the  denominations  of  all  Certificates  of  the  Class  to  which  this
Certificate belongs) in certain monthly  distributions with respect to a Trust
Fund  consisting  primarily of the Mortgage  Loans  deposited by Credit Suisse
First Boston Mortgage  Securities Corp. (the "Depositor").  The Trust Fund was
created pursuant to a Pooling and Servicing  Agreement dated as of the Cut-off
Date  specified  above (the  "Agreement")  among  Credit  Suisse  First Boston
Mortgage  Securities  Corp.,  as  depositor,  DLJ Mortgage  Capital,  Inc., as
seller,  Wells Fargo Bank,  N.A.,  as trust  administrator,  master  servicer,
servicer and back-up  servicer  and HSBC Bank USA,  National  Association,  as
trustee,  Wilshire Credit Corporation,  as special servicer,  Select Portfolio
Servicing,  Inc., as a servicer,  and the other servicers that are signatories
thereto.  To the extent not defined herein,  the capitalized terms used herein
have the  meanings  assigned  in the  Agreement.  This  Certificate  is issued
under  and  is  subject  to  the  terms,  provisions  and  conditions  of  the
Agreement,  to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound.

            Any  distribution  of the proceeds of any remaining  assets of the
Trust  Fund will be made only upon  presentment  and  surrender  of this Class
AR-L  Certificate  at the  Corporate  Trust  Office  or the  office  or agency
maintained by the Trust Administrator in New York, New York.

      Pursuant  to  Section 6.02(f)  of the  Agreement,  no  transfer  of this
Residual  Certificate  shall be made unless the Trustee  shall have received a
representation  letter from the transferee of such Certificate,  acceptable to
and in form and  substance  satisfactory  to the Trust  Administrator,  to the
effect that such  transferee  is not an employee  benefit plan or  arrangement
subject  to  Section 406  of ERISA or  Section 4975  of the Code,  or a person
using the assets of any such plan or arrangement which  representation  letter
shall not be an expense of the Trustee,  the Trust  Administrator or the Trust
Fund. In the event the  representations  referred to in the preceding sentence
are not furnished,  such  representation  shall be deemed to have been made to
the Trustee by the transferee's  acceptance of this Residual Certificate or by
any  beneficial  owner  who  purchases  an  interest  in this  Certificate  in
book-entry  form.  In the event  that a  representation  is  violated,  or any
attempt to transfer  this Residual  Certificate  to a plan or  arrangement  or
person using a plan's or  arrangement's  assets is  attempted,  the  attempted
transfer or acquisition of this Certificate shall be void and of no effect.

            Each Holder of this Class AR-L  Certificate will be deemed to have
agreed to be bound by the  restrictions  of the  Agreement,  including but not
limited to the  restrictions  that (i) each person  holding or  acquiring  any
Ownership  Interest  in  this  Class  AR-L  Certificate  must  be a  Permitted
Transferee,  (ii) no Ownership  Interest in this Class AR-L Certificate may be
transferred  without  delivery  to  the  Trust  Administrator  of  a  transfer
affidavit  of  the  initial  owner  or the  proposed  transferee  in the  form
described  in the  Agreement,  (iii)  each  person  holding or  acquiring  any
Ownership  Interest  in this  Class AR-L  Certificate  must agree to require a
transfer  affidavit  from any other  person to whom such  person  attempts  to
Transfer its  Ownership  Interest in this Class AR-L  Certificate  as required
pursuant to the Agreement,  (iv) each person holding or acquiring an Ownership
Interest  in this  Class  AR-L  Certificate  must  agree  not to  transfer  an
Ownership  Interest in this Class AR-L  Certificate if it has actual knowledge
that  the  proposed  transferee  is not a  Permitted  Transferee  and  (v) any
attempted or purported  transfer of any Ownership  Interest in this Class AR-L
Certificate  in violation of such  restrictions  will be  absolutely  null and
void and will vest no rights in the purported transferee.

            Reference  is  hereby  made  to the  further  provisions  of  this
Certificate set forth on the reverse hereof,  which further  provisions  shall
for all purposes have the same effect as if set forth at this place.

            This  Certificate  shall not be entitled to any benefit  under the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

              IN  WITNESS  WHEREOF,  the Trust  Administrator  has  caused  this
Certificate to be duly executed.

Dated: __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By _______________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

               CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                  Class AR-L

            This   Certificate   is  one  of  a  duly   authorized   issue  of
Certificates  designated  as Credit  Suisse First Boston  Mortgage  Securities
Corp., Adjustable Rate CSFB Mortgage-Backed Pass-Through Certificates,  Series
2005-1,  of the  Series  specified  on the face  hereof  (herein  collectively
called the  "Certificates"),  and representing a beneficial ownership interest
in the Trust Fund created by the Agreement.

            The  Certificateholder,  by its  acceptance  of this  Certificate,
agrees  that it will look  solely to the funds on deposit  in the  Certificate
Account  for  payment  hereunder  and that  neither  the Trustee nor the Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

            This  Certificate  does not purport to summarize the Agreement and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

            Pursuant to the terms of the  Agreement,  a  distribution  will be
made on the 25th day of each  month,  or, if such  25th day is not a  Business
Day, the Business Day immediately  following such 25th day (the  "Distribution
Date"),  commencing  on the  first  Distribution  Date  specified  on the face
hereof,  to the Person in whose name this  Certificate  is  registered  at the
close of business  on the  applicable  Record  Date in an amount  equal to the
product of the  Percentage  Interest  evidenced  by this  Certificate  and the
amount  required to be distributed to Holders of  Certificates of the Class to
which this  Certificate  belongs on such  Distribution  Date  pursuant  to the
Agreement.  The Record Date applicable to each  Distribution  Date is the last
day of the calendar month preceding the month in which such  Distribution Date
occurs.

            Distributions on this  Certificate  shall be made by wire transfer
of immediately  available  funds to the account of the Holder hereof at a bank
or   other   entity   having   appropriate   facilities   therefor,   if  such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

            The Agreement  permits,  with certain exceptions therein provided,
the amendment  thereof and the  modification  of the rights and obligations of
the Trustee, the Trust Administrator and the rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicer,  the  Seller,  the  Trustee  and the  Trust  Administrator  with the
consent of the Holders of Certificates  affected by such amendment  evidencing
the requisite  Percentage  Interest,  as provided in the  Agreement.  Any such
consent by the Holder of this  Certificate  shall be conclusive and binding on
such  Holder  and upon  all  future  Holders  of this  Certificate  and of any
Certificate  issued upon the  transfer  hereof or in  exchange  therefor or in
lieu  hereof  whether  or not  notation  of such  consent  is made  upon  this
Certificate.  The  Agreement  also permits the amendment  thereof,  in certain
limited  circumstances,  without  the  consent  of the  Holders  of any of the
Certificates.

            As provided in the  Agreement  and subject to certain  limitations
therein set forth,  the transfer of this  Certificate  is  registrable  in the
Certificate  Register  of the  Trust  Administrator  upon  surrender  of  this
Certificate for  registration of transfer at the Corporate Trust Office or the
office or agency maintained by the Trust  Administrator in New York, New York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

            The  Certificates  are issuable  only as  registered  Certificates
without coupons in  denominations  specified in the Agreement.  As provided in
the  Agreement  and  subject  to  certain   limitations   therein  set  forth,
Certificates  are  exchangeable  for new  Certificates  of the  same  Class in
authorized   denominations  and  evidencing  the  same  aggregate   Percentage
Interest, as requested by the Holder surrendering the same.

            No  service  charge  will be made  for any  such  registration  of
transfer or exchange,  but the Trust  Administrator  may require  payment of a
sum  sufficient  to cover  any tax or other  governmental  charge  payable  in
connection therewith.

            The Depositor,  the Servicer, the Master Servicer, the Seller, the
Trustee  and the  Trust  Administrator  and any  agent of the  Depositor,  the
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicer,  the  Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

            On any  Distribution  Date on which the aggregate Stated Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to ___________________________________________________________
_____________________________________________________________________________,
_____________________________________________________________________________,
for the account of ___________________________________________________________
account number _______________, or, if mailed by check, to____________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to_____________________________________
______________________________________________________________________________
______________________________________________________________________________
This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                  EXHIBIT E

                         FORM OF CLASS P CERTIFICATE

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

THIS  CERTIFICATE IS SUBORDINATED IN RIGHT OF PAYMENT TO CERTAIN  CERTIFICATES
AS DESCRIBED IN THE AGREEMENT REFERRED TO HEREIN.

THIS  CERTIFICATE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED  ("THE  ACT").  ANY RESALE OR  TRANSFER  OF THIS  CERTIFICATE  WITHOUT
REGISTRATION  THEREOF UNDER THE ACT MAY ONLY BE MADE IN A TRANSACTION EXEMPTED
FROM  THE  REGISTRATION  REQUIREMENTS  OF THE ACT AND IN  ACCORDANCE  WITH THE
PROVISIONS OF THE AGREEMENT REFERRED TO HEREIN.

PURSUANT TO SECTION  6.02(f) OF THE AGREEMENT,  NEITHER THIS  CERTIFICATE  NOR
ANY INTEREST HEREIN MAY BE TRANSFERRED  UNLESS THE TRANSFEREE  DELIVERS TO THE
TRUSTEE (I) A REPRESENTATION  LETTER TO THE EFFECT THAT SUCH TRANSFEREE IS NOT
AN EMPLOYEE  BENEFIT PLAN OR  ARRANGEMENT  SUBJECT TO THE EMPLOYEE  RETIREMENT
INCOME SECURITY ACT OF 1974, AS AMENDED  ("ERISA") OR SECTION 4975 OF THE CODE
OR A PERSON  USING THE  ASSETS OF SUCH A PLAN OR  ARRANGEMENT,  OR (II) IF THE
PURCHASER IS AN INSURANCE  COMPANY AND THE CERTIFICATE HAS BEEN THE SUBJECT OF
AN  ERISA-QUALIFYING  UNDERWRITING,  A  REPRESENTATION  IN ACCORDANCE WITH THE
PROVISIONS OF THE AGREEMENT  REFERRED TO HEREIN OR (III) AN OPINION OF COUNSEL
IN ACCORDANCE  WITH THE  PROVISIONS OF THE  AGREEMENT  REFERRED TO HEREIN.  IN
THE EVENT THE  REPRESENTATIONS  REFERRED TO IN THE PRECEDING  SENTENCE ARE NOT
FURNISHED,  SUCH  REPRESENTATION  SHALL BE  DEEMED  TO HAVE  BEEN  MADE TO THE
TRUSTEE  BY  THE  TRANSFEREE'S  ACCEPTANCE  OF  THIS  CERTIFICATE,  OR BY  ANY
BENEFICIAL  OWNER WHO PURCHASES AN INTEREST IN THIS  CERTIFICATE IN BOOK-ENTRY
FORM.  IN THE EVENT  THAT A  REPRESENTATION  IS  VIOLATED,  OR ANY  ATTEMPT TO
TRANSFER THIS  CERTIFICATE TO A PLAN OR ARRANGEMENT OR PERSON ACTING ON BEHALF
OF A PLAN OR USING A PLAN'S OR ARRANGEMENT'S  ASSETS IS ATTEMPTED  WITHOUT THE
DELIVERY  TO THE  TRUSTEE  OF THE  OPINION  OF COUNSEL  DESCRIBED  ABOVE,  THE
ATTEMPTED  TRANSFER OR ACQUISITION OF THIS CERTIFICATE SHALL BE VOID AND OF NO
EFFECT.

THIS  CERTIFICATE  HAS  NO  PRINCIPAL  BALANCE  AND  IS  NOT  ENTITLED  TO ANY
DISTRIBUTIONS IN RESPECT OF PRINCIPAL.

  Certificate No.                     :     P-1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Percentage Interest                 :     ____%

CUSIP                               :     007036 EL 6

Maturity Date                       :     May 2035

               CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
  Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1,
                                   Class P

      evidencing  a  100%  Percentage   Interest  in  the  distributions
      allocable  to the  Class P  Certificates  with  respect to a Trust
      Fund   consisting   primarily  of  a  pool  of   adjustable   rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      This  Certificate does not evidence an obligation of, or an interest in,
and is not guaranteed by the Depositor,  the Seller, the Master Servicer,  the
Servicers,  the  Special  Servicer,  the  Trustee  or the Trust  Administrator
referred  to  below  or any  of  their  respective  affiliates.  Neither  this
Certificate   nor  the  Mortgage  Loans  are  guaranteed  or  insured  by  any
governmental agency or instrumentality.

      This  certifies  that  _____________________________,  is the registered
owner of the Percentage  Interest  evidenced by this Certificate  (obtained by
dividing  the  denomination  of  this  Certificate  by  the  aggregate  of the
denominations  of all  Certificates  of the  Class to which  this  Certificate
belongs)  in  certain  monthly  distributions  with  respect  to a Trust  Fund
consisting  primarily of the Mortgage  Loans  deposited by Credit Suisse First
Boston  Mortgage  Securities  Corp.  (the  "Depositor").  The  Trust  Fund was
created pursuant to a Pooling and Servicing  Agreement dated as of the Cut-off
Date  specified  above (the  "Agreement")  among  Credit  Suisse  First Boston
Mortgage  Securities  Corp.,  as  depositor,  DLJ Mortgage  Capital,  Inc., as
seller,  Wells Fargo Bank,  N.A.,  as trust  administrator,  master  servicer,
servicer and back-up  servicer  and HSBC Bank USA,  National  Association,  as
trustee,  Wilshire Credit Corporation,  as special servicer,  Select Portfolio
Servicing,  Inc., as a servicer,  and the other servicers that are signatories
thereto.  To the extent not defined herein,  the capitalized terms used herein
have the  meanings  assigned  in the  Agreement.  This  Certificate  is issued
under  and  is  subject  to  the  terms,  provisions  and  conditions  of  the
Agreement,  to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound.

      No transfer of this  Certificate  shall be made unless such  transfer is
made pursuant to an effective  registration statement under the Securities Act
and any applicable  state  securities laws or is exempt from the  registration
requirements  under  said Act and such laws.  In the event that a transfer  is
to be made in reliance  upon an  exemption  from the  Securities  Act and such
laws, in order to assure  compliance  with the  Securities  Act and such laws,
the   Certificateholder   desiring   to   effect   such   transfer   and  such
Certificateholder's  prospective  transferee  shall each  certify to the Trust
Administrator in writing the facts  surrounding the transfer and (i) deliver a
letter in  substantially  the form of either  Exhibit L and either (A) Exhibit
M-1,  provided that all of the  Certificates of the Class shall be transferred
to one investor or the Depositor  otherwise consents to such transfer,  or (B)
Exhibit M-2 or (ii) there shall be  delivered  to the Trust  Administrator  at
the expense of the  transferor an Opinion of Counsel that such transfer may be
made  pursuant to an exemption  from the  Securities  Act.  The Holder  hereof
desiring to effect such transfer  shall,  and does hereby agree to,  indemnify
the Trustee,  the Trust  Administrator and the Depositor against any liability
that may result if the transfer is not so exempt or is not made in  accordance
with such federal and state laws.

      Pursuant  to  Section 6.02(f)  of  the  Agreement,  no  transfer  of  an
ERISA-Restricted  Certificate  shall be made  unless  the  Trustee  shall have
received  either  (i) a  representation  letter  from the  transferee  of such
ERISA-Restricted  Certificate,   acceptable  to  and  in  form  and  substance
satisfactory  to the Trust  Administrator,  to the effect that such transferee
is not an employee  benefit  plan or  arrangement  subject to  Section 406  of
ERISA or  Section 4975  of the Code,  or a person using the assets of any such
plan or  arrangement  which  representation  letter shall not be an expense of
the Trustee,  the Trust Administrator or the Trust Fund, (ii) if the purchaser
is an  insurance  company and the  ERISA-Restricted  Certificate  has been the
subject  of  an  ERISA-Qualifying  Underwriting,  a  representation  that  the
purchaser is an insurance  company which is purchasing such  Certificates with
funds  contained in an "insurance  company  general  account" (as such term is
defined in  Section V(e)  of  Prohibited  Transaction  Class  Exemption  95-60
("PTCE  95-60"))  and that the purchase  and holding of such  Certificate  are
covered  under  Sections  I and III of PTCE  95-60 or (iii) in the case of any
such  ERISA-Restricted  Certificate  presented for registration in the name of
an employee  benefit  plan  subject to ERISA or  Section 4975  of the Code (or
comparable  provisions of any subsequent  enactments),  or a person using such
plan's or  arrangement's  assets,  an Opinion of Counsel  satisfactory  to the
Trust  Administrator  to the  effect  that the  purchase  or  holding  of such
Certificate will not result in prohibited  transactions  under  Section 406 of
ERISA and/or Section 4975 of the Code and will not subject the Depositor,  the
Trustee,  the Trust  Administrator,  the Master Servicer or any other Servicer
to any  obligation in addition to those  undertaken in this  Agreement,  which
Opinion  of  Counsel  shall not be an  expense  of such  parties  or the Trust
Fund. In the event the  representations  referred to in the preceding sentence
are not furnished,  such  representation  shall be deemed to have been made to
the Trustee by the transferee's acceptance of an ERISA-Restricted  Certificate
or by any  beneficial  owner who purchases an interest in this  certificate in
book-entry  form.  In the event  that a  representation  is  violated,  or any
attempt to transfer an  ERISA-Restricted  Certificate to a plan or arrangement
or person  using a plan's or  arrangement's  assets is  attempted  without the
delivery  to the  Trustee  of the  Opinion  of Counsel  described  above,  the
attempted  transfer or acquisition of this certificate shall be void and of no
effect.

      Reference is hereby made to the further  provisions of this  Certificate
set forth following the signature page hereof,  which further provisions shall
for all purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  _______________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By _______________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

               CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
  Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1,
                                   Class P

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable  Rate Mortgage  Trust 2005-1,  of the Series  specified on the face
hereof (herein  collectively  called the  "Certificates"),  and representing a
beneficial ownership interest in the Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The Depositor,  each Servicer,  the Master  Servicer,  each Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,  the  Master  Servicer,  each  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
 Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to ___________________________________________________________
_____________________________________________________________________________,
_____________________________________________________________________________,
for the account of ___________________________________________________________
account number _______________, or, if mailed by check, to____________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to_____________________________________
______________________________________________________________________________
______________________________________________________________________________
This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                  EXHIBIT F

                        FORM OF CLASS 5-X CERTIFICATE

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

THIS  CERTIFICATE IS SUBORDINATED IN RIGHT OF PAYMENT TO CERTAIN  CERTIFICATES
AS DESCRIBED IN THE AGREEMENT REFERRED TO HEREIN.

THIS  CERTIFICATE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED  ("THE  ACT").  ANY RESALE OR  TRANSFER  OF THIS  CERTIFICATE  WITHOUT
REGISTRATION  THEREOF UNDER THE ACT MAY ONLY BE MADE IN A TRANSACTION EXEMPTED
FROM  THE  REGISTRATION  REQUIREMENTS  OF THE ACT AND IN  ACCORDANCE  WITH THE
PROVISIONS OF THE AGREEMENT REFERRED TO HEREIN.

PURSUANT TO SECTION  6.02(f) OF THE AGREEMENT,  NEITHER THIS  CERTIFICATE  NOR
ANY INTEREST HEREIN MAY BE TRANSFERRED  UNLESS THE TRANSFEREE  DELIVERS TO THE
TRUSTEE (I) A REPRESENTATION  LETTER TO THE EFFECT THAT SUCH TRANSFEREE IS NOT
AN EMPLOYEE  BENEFIT PLAN OR  ARRANGEMENT  SUBJECT TO THE EMPLOYEE  RETIREMENT
INCOME SECURITY ACT OF 1974, AS AMENDED  ("ERISA") OR SECTION 4975 OF THE CODE
OR A PERSON  USING THE  ASSETS OF SUCH A PLAN OR  ARRANGEMENT,  OR (II) IF THE
PURCHASER IS AN INSURANCE  COMPANY AND THE CERTIFICATE HAS BEEN THE SUBJECT OF
AN  ERISA-QUALIFYING  UNDERWRITING,  A  REPRESENTATION  IN ACCORDANCE WITH THE
PROVISIONS OF THE AGREEMENT  REFERRED TO HEREIN OR (III) AN OPINION OF COUNSEL
IN ACCORDANCE  WITH THE  PROVISIONS OF THE  AGREEMENT  REFERRED TO HEREIN.  IN
THE EVENT THE  REPRESENTATIONS  REFERRED TO IN THE PRECEDING  SENTENCE ARE NOT
FURNISHED,  SUCH  REPRESENTATION  SHALL BE  DEEMED  TO HAVE  BEEN  MADE TO THE
TRUSTEE  BY  THE  TRANSFEREE'S  ACCEPTANCE  OF  THIS  CERTIFICATE,  OR BY  ANY
BENEFICIAL  OWNER WHO PURCHASES AN INTEREST IN THIS  CERTIFICATE IN BOOK-ENTRY
FORM.  IN THE EVENT  THAT A  REPRESENTATION  IS  VIOLATED,  OR ANY  ATTEMPT TO
TRANSFER THIS  CERTIFICATE TO A PLAN OR ARRANGEMENT OR PERSON ACTING ON BEHALF
OF A PLAN OR USING A PLAN'S OR ARRANGEMENT'S  ASSETS IS ATTEMPTED  WITHOUT THE
DELIVERY  TO THE  TRUSTEE  OF THE  OPINION  OF COUNSEL  DESCRIBED  ABOVE,  THE
ATTEMPTED  TRANSFER OR ACQUISITION OF THIS CERTIFICATE SHALL BE VOID AND OF NO
EFFECT.

THIS  CERTIFICATE  HAS  NO  PRINCIPAL  BALANCE  AND  IS  NOT  ENTITLED  TO ANY
DISTRIBUTIONS IN RESPECT OF PRINCIPAL.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Notional Amount of this
Certificate ("Denomination")        :     $0

Initial Class Notional Amount of
all Certificates of this Class      :     $0

Percentage Interest                 :     100%

CUSIP                               :

Pass-Through Rate                   :     N/A

Maturity Date                       :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                  Class 5-X

      evidencing  a  100%  Percentage   Interest  in  the  distributions
      allocable to the  Class 5-X  Certificates  with respect to a Trust
      Fund   consisting   primarily  of  a  pool  of   adjustable   rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      This  Certificate does not evidence an obligation of, or an interest in,
and is not guaranteed by the Depositor,  the Seller, the Master Servicer,  the
Servicers,  the  Special  Servicer,  the  Trustee  or the Trust  Administrator
referred  to  below  or any  of  their  respective  affiliates.  Neither  this
Certificate   nor  the  Mortgage  Loans  are  guaranteed  or  insured  by  any
governmental agency or instrumentality.

      This certifies that [_____________________________________________],  is
the registered owner of the Percentage  Interest evidenced by this Certificate
(obtained by dividing the  denomination  of this  Certificate by the aggregate
of  the  denominations  of  all  Certificates  of  the  Class  to  which  this
Certificate belongs) in certain monthly  distributions with respect to a Trust
Fund  consisting  primarily of the Mortgage  Loans  deposited by Credit Suisse
First Boston Mortgage  Securities Corp. (the "Depositor").  The Trust Fund was
created pursuant to a Pooling and Servicing  Agreement dated as of the Cut-off
Date  specified  above (the  "Agreement")  among  Credit  Suisse  First Boston
Mortgage  Securities  Corp.,  as  depositor,  DLJ Mortgage  Capital,  Inc., as
seller,  Wells Fargo Bank,  N.A.,  as trust  administrator,  master  servicer,
servicer and back-up  servicer  and HSBC Bank USA,  National  Association,  as
trustee,  Wilshire Credit Corporation,  as special servicer,  Select Portfolio
Servicing,  Inc., as a servicer,  and the other servicers that are signatories
thereto.  To the extent not defined herein,  the capitalized terms used herein
have the  meanings  assigned  in the  Agreement.  This  Certificate  is issued
under  and  is  subject  to  the  terms,  provisions  and  conditions  of  the
Agreement,  to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound.

      No transfer of this  Certificate  shall be made unless such  transfer is
made pursuant to an effective  registration statement under the Securities Act
and any applicable  state  securities laws or is exempt from the  registration
requirements  under  said Act and such laws.  In the event that a transfer  is
to be made in reliance  upon an  exemption  from the  Securities  Act and such
laws, in order to assure  compliance  with the  Securities  Act and such laws,
the   Certificateholder   desiring   to   effect   such   transfer   and  such
Certificateholder's  prospective  transferee  shall each  certify to the Trust
Administrator in writing the facts  surrounding the transfer and (i) deliver a
letter in substantially the form of either Exhibit L and either  (A) Exhibit M
1, provided that all of the  Certificates of the Class shall be transferred to
one investor or the  Depositor  otherwise  consents to such  transfer,  or (B)
Exhibit M 2 or (ii) there shall be  delivered  to the Trust  Administrator  at
the expense of the  transferor an Opinion of Counsel that such transfer may be
made  pursuant to an exemption  from the  Securities  Act.  The Holder  hereof
desiring to effect such transfer  shall,  and does hereby agree to,  indemnify
the Trustee,  the Trust  Administrator and the Depositor against any liability
that may result if the transfer is not so exempt or is not made in  accordance
with such federal and state laws.

      Pursuant  to  Section 6.02(f)  of  the  Agreement,  no  transfer  of  an
ERISA-Restricted  Certificate  shall be made  unless  the  Trustee  shall have
received  either  (i) a  representation  letter  from the  transferee  of such
ERISA-Restricted  Certificate,   acceptable  to  and  in  form  and  substance
satisfactory  to the Trust  Administrator,  to the effect that such transferee
is not an employee  benefit  plan or  arrangement  subject to  Section 406  of
ERISA or  Section 4975  of the Code,  or a person using the assets of any such
plan or  arrangement  which  representation  letter shall not be an expense of
the Trustee,  the Trust Administrator or the Trust Fund, (ii) if the purchaser
is an  insurance  company and the  ERISA-Restricted  Certificate  has been the
subject  of  an  ERISA-Qualifying  Underwriting,  a  representation  that  the
purchaser is an insurance  company which is purchasing such  Certificates with
funds  contained in an "insurance  company  general  account" (as such term is
defined in  Section V(e)  of  Prohibited  Transaction  Class  Exemption  95-60
("PTCE  95-60"))  and that the purchase  and holding of such  Certificate  are
covered  under  Sections  I and III of PTCE  95-60 or (iii) in the case of any
such  ERISA-Restricted  Certificate  presented for registration in the name of
an employee  benefit  plan  subject to ERISA or  Section 4975  of the Code (or
comparable  provisions of any subsequent  enactments),  or a person using such
plan's or  arrangement's  assets,  an Opinion of Counsel  satisfactory  to the
Trust  Administrator  to the  effect  that the  purchase  or  holding  of such
Certificate will not result in prohibited  transactions  under  Section 406 of
ERISA and/or Section 4975 of the Code and will not subject the Depositor,  the
Trustee,  the Trust  Administrator,  the Master Servicer or any other Servicer
to any  obligation in addition to those  undertaken in this  Agreement,  which
Opinion  of  Counsel  shall not be an  expense  of such  parties  or the Trust
Fund. In the event the  representations  referred to in the preceding sentence
are not furnished,  such  representation  shall be deemed to have been made to
the Trustee by the transferee's acceptance of an ERISA-Restricted  Certificate
or by any  beneficial  owner who purchases an interest in this  certificate in
book-entry  form.  In the event  that a  representation  is  violated,  or any
attempt to transfer an  ERISA-Restricted  Certificate to a plan or arrangement
or person  using a plan's or  arrangement's  assets is  attempted  without the
delivery  to the  Trustee  of the  Opinion  of Counsel  described  above,  the
attempted  transfer or acquisition of this certificate shall be void and of no
effect.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By _______________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                  Class 5-X

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed  Pass-Through Certificates,  Series 2005-1, of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

______________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to ___________________________________________________________
_____________________________________________________________________________,
_____________________________________________________________________________,
for the account of ___________________________________________________________
account number _______________, or, if mailed by check, to____________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to_____________________________________
______________________________________________________________________________
______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                  EXHIBIT G

                       FORM OF CLASS C-B-1X CERTIFICATE

UNLESS THIS  CERTIFICATE IS PRESENTED BY AN AUTHORIZED  REPRESENTATIVE  OF THE
DEPOSITORY  TRUST COMPANY,  A NEW YORK CORPORATION  ("DTC"),  TO ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER,  EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS  REGISTERED  IN THE NAME OF CEDE & CO. OR IN SUCH  OTHER  NAME AS IS
REQUESTED BY AN AUTHORIZED  REPRESENTATIVE  OF DTC (AND ANY PAYMENT IS MADE TO
CEDE  &  CO.  OR  TO  SUCH  OTHER  ENTITY  AS IS  REQUESTED  BY AN  AUTHORIZED
REPRESENTATIVE  OF DTC), ANY TRANSFER,  PLEDGE,  OR OTHER USE HEREOF FOR VALUE
OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL  INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

SOLELY FOR U.S.  FEDERAL  INCOME TAX  PURPOSES,  THIS  CERTIFICATE  REPRESENTS
OWNERSHIP  OF A  "REGULAR  INTEREST"  IN A "REAL  ESTATE  MORTGAGE  INVESTMENT
CONDUIT," AS THOSE TERMS ARE DEFINED,  RESPECTIVELY, IN SECTIONS 860G AND 860D
OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE "CODE").

THIS  CERTIFICATE  HAS  NO  PRINCIPAL  BALANCE  AND  IS  NOT  ENTITLED  TO ANY
DISTRIBUTIONS IN RESPECT OF PRINCIPAL.

--------------------------------------------------------------------------------

Certificate No.                     :     1

Cut-off Date                        :     January 1, 2005

First Distribution Date             :     February 25, 2005

Initial Notional Amount of this
Certificate ("Denomination")        :     $

Initial Class Notional Amount of
all Certificates of this Class      :     $

Percentage Interest                 :     100%

CUSIP                               :

Pass-Through Rate                   :     Variable

Maturity Date                       :     May 2035

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                 Class C-B-1X

      evidencing  a  100%  Percentage   Interest  in  the  distributions
      allocable  to the Class  C-B-1X  Certificates  with  respect  to a
      Trust  Fund  consisting  primarily  of a pool of  adjustable  rate
      conventional  mortgage  loans (the  "Mortgage  Loans")  secured by
      first liens on one- to four-family residential properties.

      Credit Suisse First Boston Mortgage Securities Corp., as Depositor

      This  Certificate does not evidence an obligation of, or an interest in,
and is not guaranteed by the Depositor,  the Seller, the Master Servicer,  the
Servicers,  the  Special  Servicer,  the  Trustee  or the Trust  Administrator
referred  to  below  or any  of  their  respective  affiliates.  Neither  this
Certificate   nor  the  Mortgage  Loans  are  guaranteed  or  insured  by  any
governmental agency or instrumentality.

      This certifies  that  CEDE  &  CO., is the registered  owner  of the
Percentage  Interest  evidenced by this Certificate  (obtained by dividing the
denomination of this Certificate by the aggregate of the  denominations of all
Certificates  of the  Class to which  this  Certificate  belongs)  in  certain
monthly  distributions  with respect to a Trust Fund  consisting  primarily of
the  Mortgage  Loans   deposited  by  Credit  Suisse  First  Boston   Mortgage
Securities Corp. (the  "Depositor").  The Trust Fund was created pursuant to a
Pooling and Servicing  Agreement  dated as of the Cut-off Date specified above
(the "Agreement") among Credit Suisse First Boston Mortgage  Securities Corp.,
as depositor,  DLJ Mortgage Capital,  Inc., as seller, Wells Fargo Bank, N.A.,
as trust  administrator,  master  servicer,  servicer and back-up servicer and
HSBC Bank USA, National Association,  as trustee, Wilshire Credit Corporation,
as special servicer, Select Portfolio Servicing,  Inc., as a servicer, and the
other  servicers  that are  signatories  thereto.  To the extent  not  defined
herein,  the capitalized  terms used herein have the meanings  assigned in the
Agreement.  This  Certificate  is issued  under and is  subject  to the terms,
provisions and conditions of the Agreement,  to which  Agreement the Holder of
this Certificate by virtue of the acceptance  hereof assents and by which such
Holder is bound.

      Reference is hereby made to the further  provisions of this  Certificate
set  forth on the  reverse  hereof,  which  further  provisions  shall for all
purposes have the same effect as if set forth at this place.

      This  Certificate  shall  not be  entitled  to  any  benefit  under  the
Agreement  or be valid for any purpose  unless  manually  countersigned  by an
authorized signatory of the Trust Administrator.

--------------------------------------------------------------------------------

      IN WITNESS WHEREOF,  the Trust Administrator has caused this Certificate
to be duly executed.

Dated:  __________________

                                    WELLS FARGO BANK, N.A.
                                    as Trust Administrator

                                    By________________________________________
Countersigned:

By ___________________________
      Authorized Signatory of
      WELLS FARGO BANK, N.A.
      as Trust Administrator

--------------------------------------------------------------------------------

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                    Adjustable Rate Mortgage Trust 2005-1,
   Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series 2005-1
                                 Class C-B-1X

      This  Certificate  is one of a duly  authorized  issue  of  Certificates
designated  as  Credit  Suisse  First  Boston   Mortgage   Securities   Corp.,
Adjustable Rate Mortgage-Backed  Pass-Through Certificates,  Series 2005-1, of
the  Series  specified  on the face  hereof  (herein  collectively  called the
"Certificates"),  and  representing  a  beneficial  ownership  interest in the
Trust Fund created by the Agreement.

      The  Certificateholder,  by its acceptance of this  Certificate,  agrees
that it will look  solely to the funds on deposit in the  Certificate  Account
for   payment   hereunder   and  that   neither  the  Trustee  nor  the  Trust
Administrator  is  liable to the  Certificateholders  for any  amount  payable
under this  Certificate  or the Agreement or, except as expressly  provided in
the Agreement, subject to any liability under the Agreement.

      This  Certificate  does not  purport  to  summarize  the  Agreement  and
reference is made to the Agreement for the interests,  rights and  limitations
of  rights,  benefits,  obligations  and  duties  evidenced  thereby,  and the
rights, duties and immunities of the Trustee and the Trust Administrator.

      Pursuant to the terms of the Agreement,  a distribution  will be made on
the 25th day of each month,  or, if such 25th day is not a Business  Day,  the
Business Day immediately  following (the "Distribution  Date"),  commencing on
the first  Distribution  Date  specified on the face hereof,  to the Person in
whose name this  Certificate  is  registered  at the close of  business on the
applicable  Record Date in an amount  equal to the  product of the  Percentage
Interest  evidenced  by  this  Certificate  and  the  amount  required  to  be
distributed to Holders of Certificates of the Class to which this  Certificate
belongs on such Distribution  Date pursuant to the Agreement.  The Record Date
applicable to each  Distribution  Date is (1) with respect to all Certificates
other than the LIBOR  Certificates  held in Book-Entry  Form,  the last day of
the calendar month preceding the month in which such  Distribution Date occurs
and (2) with respect to the LIBOR  Certificates  held in Book-Entry Form only,
the  close  of  business  on the  last  Business  Day of  the  calendar  month
immediately preceding the calendar month of such Distribution Date.

      Distributions  on this  Certificate  shall be made by wire  transfer  of
immediately  available  funds to the account of the Holder hereof at a bank or
other   entity   having    appropriate    facilities    therefor,    if   such
Certificateholder  shall have so notified the Trust  Administrator  in writing
at  least  five  Business  Days  prior  to the  related  Record  Date and such
Certificateholder  shall  satisfy  the  conditions  to  receive  such  form of
payment  set  forth in the  Agreement,  or, if not,  by check  mailed by first
class  mail  to  the  address  of  such  Certificateholder  appearing  in  the
Certificate  Register.  The final  distribution  on each  Certificate  will be
made  in  like  manner,  but  only  upon  presentment  and  surrender  of such
Certificate at the Corporate Trust Office or such other location  specified in
the notice to Certificateholders of such final distribution.

      The Agreement permits,  with certain  exceptions  therein provided,  the
amendment  thereof and the  modification  of the rights and obligations of the
Trustee,  the Trust  Administrator  and the  rights of the  Certificateholders
under the Agreement at any time by the  Depositor,  the Master  Servicer,  the
Servicers,  the  Special  Servicer,  the  Seller,  the  Trustee  and the Trust
Administrator  with the  consent of the  Holders of  Certificates  affected by
such amendment evidencing the requisite  Percentage  Interest,  as provided in
the  Agreement.  Any such consent by the Holder of this  Certificate  shall be
conclusive  and  binding on such  Holder  and upon all future  Holders of this
Certificate  and of any  Certificate  issued  upon the  transfer  hereof or in
exchange  therefor or in lieu hereof  whether or not  notation of such consent
is made upon this  Certificate.  The  Agreement  also  permits  the  amendment
thereof, in certain limited circumstances,  without the consent of the Holders
of any of the Certificates.

      As provided in the Agreement and subject to certain  limitations therein
set forth,  the transfer of this Certificate is registrable in the Certificate
Register of the Trust  Administrator  upon surrender of this  Certificate  for
registration  of  transfer  at the  Corporate  Trust  Office or the  office or
agency  maintained  by  the  Trust   Administrator  in  New  York,  New  York,
accompanied by a written  instrument of transfer in form  satisfactory  to the
Trust Administrator and the Certificate  Registrar duly executed by the holder
hereof or such  holder's  attorney duly  authorized in writing,  and thereupon
one or more new  Certificates  of the same Class in  authorized  denominations
and evidencing the same aggregate  Percentage  Interest in the Trust Fund will
be issued to the designated transferee or transferees.

      The  Certificates are issuable only as registered  Certificates  without
coupons in  denominations  specified  in the  Agreement.  As  provided  in the
Agreement and subject to certain limitations  therein set forth,  Certificates
are  exchangeable  for  new  Certificates  of the  same  Class  in  authorized
denominations  and  evidencing  the same  aggregate  Percentage  Interest,  as
requested by the Holder surrendering the same.

      No service charge will be made for any such  registration of transfer or
exchange,  but the Trust Administrator may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

      The  Depositor,  each Servicer,  the Master  Servicer,  the Seller,  the
Trustee  and the  Trust  Administrator  and any agent of the  Depositor,  each
Servicer,   the  Master  Servicer,  the  Seller,  the  Trustee  or  the  Trust
Administrator  may  treat  the  Person  in  whose  name  this  Certificate  is
registered  as the owner hereof for all purposes,  and none of the  Depositor,
the  Servicers,  the Master  Servicer,  the  Seller,  the  Trustee,  the Trust
Administrator  or any  such  agent  shall be  affected  by any  notice  to the
contrary.

      On any  Distribution  Date  on  which  the  aggregate  Stated  Principal
Balance  of the  Mortgage  Loans in Group 1,  Group 2, Group 3, and Group 4 is
equal to 10% or less of the sum of the Aggregate  Group 1 Collateral  Balance,
the Aggregate Group 2 Collateral  Balance and the aggregate  Stated  Principal
Balance of the Mortgage  Loans in Group 3 and Group 4 as of the Cut-off  Date,
the Terminating Entity will have the option to repurchase,  in whole, from the
Trust  Fund all  remaining  Mortgage  Loans in Group 1,  Group 2,  Group 3 and
Group 4 and all  property  acquired  in  respect of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  On any  Distribution
Date on which the aggregate Stated  Principal  Balance of the Group 5 Mortgage
Loans is equal to 10% or less of the sum of the  Aggregate  Group 5 Collateral
Balance and the  aggregate  Stated  Principal  Balance of the Group 5 Mortgage
Loans as of the Cut-off Date, the  Terminating  Entity will have the option to
repurchase,  in whole,  from the Trust  Fund all  remaining  Group 5  Mortgage
Loans  and all  property  acquired  in  respect  of such  Mortgage  Loans at a
purchase price  determined as provided in the Agreement.  In the event that no
such  optional   termination  occurs,  the  obligations  and  responsibilities
created by the  Agreement  will  terminate  upon the later of the  maturity or
other  liquidation (or any advance with respect  thereto) of the last Mortgage
Loan  remaining  in the  Trust  Fund or the  disposition  of all  property  in
respect  thereof and the  distribution  to  Certificateholders  of all amounts
required to be distributed  pursuant to the Agreement.  In no event,  however,
will the trust  created by the  Agreement  continue  beyond the earlier of (i)
the  expiration  of 21 years  from  the  death  of the  last  survivor  of the
descendants  living at the date of the Agreement of a certain  person named in
the  Agreement  or (ii) the  Distribution  Date in May  2037.  Any  term  used
herein that is defined in the  Agreement  shall have the  meaning  assigned in
the  Agreement,  and nothing  herein  shall be deemed  inconsistent  with that
meaning.

--------------------------------------------------------------------------------

                                  ASSIGNMENT

      FOR VALUE  RECEIVED,  the  undersigned  hereby  sell(s),  assign(s)  and
transfer(s) unto
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(Please  print or  typewrite  name and  address  including  postal zip code of
assignee)

the  Percentage  Interest  evidenced  by the  within  Certificate  and  hereby
authorizes  the  transfer  of  registration  of such  Percentage  Interest  to
assignee on the Certificate Register of the Trust Fund.

I (We) further direct the Trust  Administrator to issue a new Certificate of a
like  denomination  and Class,  to the above named  assignee  and deliver such
Certificate to the following address:

______________________________________________________________________________
Dated:

_____________________________________________________________________________
Signature by or on behalf of assignor

                          DISTRIBUTION INSTRUCTIONS

   The assignee should include the following for purposes of distribution:

Distributions  shall be made, by wire transfer or  otherwise,  in  immediately
available funds to ___________________________________________________________
_____________________________________________________________________________,
_____________________________________________________________________________,
for the account of ___________________________________________________________
account number _______________, or, if mailed by check, to____________________
______________________________________________________________________________
______________________________________________________________________________
Applicable statements should be mailed to_____________________________________
______________________________________________________________________________
______________________________________________________________________________

This information is provided by, the assignee named above, or, as its agent.

--------------------------------------------------------------------------------

                                  EXHIBIT H

                         FORM OF SERVICER INFORMATION

The  following  information  will be e-mailed  to the Master  Servicer by each
Servicer and to the Trust Administrator by the Master Servicer:

Servicer Loan Number
Trust Loan Number (if applicable)
Scheduled Net Interest
Scheduled Principal
Curtailment Applied
Curtailment Adjustment
Mortgage Rate
Servicing Fee Rate
P&I Payment
Beginning Scheduled Balance
Ending Scheduled Balance
Ending Actual Principal Balance
Due Date
Prepayment in full Principal
Prepayment in full Net Interest
Prepayment in full Penalty
Delinquencies:
      1-30
      31-60
      61-90
      91 +
Foreclosures
REO Properties
Loss Amounts & Loss Types (i.e., Bankruptcy, Excess, Deficient Valuation,
Debt Reduction)

Wells Fargo Bank NA
9062 Old Annapolis Road
Columbia, MD 20145
Attention:  Client Manager, CSFB ARMT 2005-1
Phone No. 410-884-2000
Fax No. 410-715-2380

[name]
Wells Fargo Bank, N.A.
[address]
Phone No. [________]
Fax No. [________]
[email]

--------------------------------------------------------------------------------

WELLS FARGO BANK, N.A.
Form 332

------------------------------------------------------------------------------
Calculation of Realized Loss

Purpose

To provide the Servicer with a form for the calculation of any Realized Loss
(or gain) as a result of a Mortgage Loan having been foreclosed and
Liquidated.

Distribution

The Servicer will prepare the form in duplicate and send the original
together with evidence of conveyance of title and appropriate supporting
documentation to the Master Servicer with the Monthly Accounting Reports
which supports the Mortgage Loan's removal from the Mortgage Loan Activity
Report.  The Servicer will retain the duplicate for its own records.

Due Date

With respect to any liquidated Mortgage Loan, the form will be submitted to
the Master Servicer no later than the date on which statements are due to the
Master Servicer under Section4.02 of this Agreement (the "Statement Date")
in the month following receipt of final liquidation proceeds and supporting
documentation relating to such liquidated Mortgage Loan; provided, that if
such Statement Date is not at least 30 days after receipt of final
liquidation proceeds and supporting documentation relating to such liquidated
Mortgage Loan, then the form will be submitted on the first Statement Date
occurring after the 30th day following receipt of final liquidation proceeds
and supporting documentation.

Preparation Instructions
The numbers on the form correspond with the numbers listed below.
1.    The actual Unpaid Principal Balance of the Mortgage Loan.
2.    The Total Interest Due less the aggregate amount of servicing fee that
      would have been earned if all delinquent payments had been made as
      agreed.
3-7.  Complete as necessary.  All line entries must be supported by copies of
      appropriate statements, vouchers, receipts, canceled checks, etc., to
      document the expense.  Entries not properly documented will not be
      reimbursed to the Servicer.
8.    Accrued Servicing Fees based upon the Scheduled Principal Balance of
      the Mortgage Loan as calculated on a monthly basis.
10.   The total of lines 1 through 9.

Credits
11-17.      Complete as necessary.  All line entries must be supported by
      copies of the appropriate claims forms, statements, payment checks,
      etc.  to document the credit.  If the Mortgage Loan is subject to a
      Bankruptcy Deficiency, the difference between the Unpaid Principal
      Balance of the Note prior to the Bankruptcy Deficiency and the Unpaid
      Principal Balance as reduced by the Bankruptcy Deficiency should be
      input on line 16.
18.   The total of lines 11 through 17.

Total Realized Loss (or Amount of Any Gain)

19.   The total derived from subtracting line 18 from 10.  If the amount
      represents a realized gain, show the amount in parenthesis (   ).

--------------------------------------------------------------------------------

                            WELLS FARGO BANK, N.A.
                         CALCULATION OF REALIZED LOSS

------------------------------------------------------------------------------

            WELLS FARGO BANK, N.A. Trust:  ___________________________
Prepared by:  __________________                      Date:  _______________
Phone:  ______________________

                              Service Loan No.          Servicer Name           Servicer Address

         -------------------       ------------------      -------------------

WELLS FARGO BANK, N.A.
Loan No._____________________________
Borrower's Name:________________________________________________________
Property
Address:________________________________________________________________
Liquidation and Acquisition Expenses:
      Actual Unpaid Principal Balance of             $ _______________(1)
      Mortgage Loan
      Interest accrued at Net Rate                    ________________(2)
      Attorney's Fees                                 ________________(3)
      Taxes                                           ________________(4)
      Property Maintenance                            ________________(5)
      MI/Hazard Insurance Premiums                    ________________(6)
      Hazard Loss Expenses                            ________________(7)
      Accrued Servicing Fees                          ________________(8)
      Other (itemize)                                 ________________(9)
                                                      $ _________________
      _________________________________________
                                                      __________________
      _________________________________________
                                                      __________________
      _________________________________________
                                                      __________________
      _________________________________________
Total Expenses                                       $ ______________(10)
Credits:
      Escrow Balance                                 $ ______________(11)
      HIP Refund                                     ________________(12)
      Rental Receipts                                ________________(13)
      Hazard Loss Proceeds                           ________________(14)
      Primary Mortgage Insurance Proceeds            ________________(15)
      Proceeds from Sale of Acquired Property        ________________(16)
      Other (itemize)                                ________________(17)
                                                      ___________________
      _________________________________________
                                                      ___________________
      _________________________________________
Total Credits                                        $________________(18)
Total Realized Loss (or Amount of Gain)              $________________(19)

--------------------------------------------------------------------------------

                                 EXHIBIT I-1

               FORM OF TRUST RECEIPT AND INITIAL CERTIFICATION

                          [_________________, 200_]

HSBC Bank USA, National Association
      as Trustee for the
Adjustable Rate Mortgage Trust 2005-1
Corporate Trust Services/CSFB ARMT 2005-1
452 Fifth Avenue
New York, New York 10018

Wells Fargo Bank, N.A.,
as Trust Administrator and Master Servicer for the
Adjustable Rate Mortgage Trust 2005-1
9062 Old Annapolis Road,
Columbia, MD 21045

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue
New York, New York 10010
Attention: Peter Sack

      Re:   Custodial Agreement,  dated as of January 1, 2005, among HSBC Bank
            USA, National Association,  as Trustee, Wells Fargo Bank, N.A., as
            Trust Administrator, and [_______________], as Custodian.

        Ladies and Gentlemen:

            In   accordance   with  the   provisions   of   Section 4  of  the
above-referenced  Custodial  Agreement,  the  undersigned,  as the  Custodian,
hereby  certifies as to each  Mortgage Loan in the Mortgage Loan Schedule that
(i) it has received  the original  Mortgage  Note and  Assignment  of Mortgage
with respect to each  Mortgage  Loan  identified on the Mortgage Loan Schedule
attached  hereto  and (ii)  such  Mortgage  Note has been  reviewed  by it and
appears  regular on its face and relates to such Mortgage  Loan. The Custodian
makes no  representations  as to (i) the validity,  legality,  enforceability,
sufficiency,  due  authorization  or  genuineness  of  any  of  the  documents
contained in each  Custodial  File or of any of the Mortgage Loans or (ii) the
collectability,   insurability,  effectiveness  or  suitability  of  any  such
Mortgage Loan.

            The  Custodian  hereby  confirms  that  it is  holding  each  such
Mortgage  Note,  Assignment  of Mortgage and  Assignment  of Note as agent and
bailee of, and custodian  for the  exclusive  use and benefit,  and subject to
the sole  direction,  of the Trustee  pursuant to the terms and  conditions of
the Custodial Agreement.

            This Trust Receipt and Initial  Certification  is not divisible or
negotiable.

            The Custodian will accept and act on instructions  with respect to
the Mortgage  Loans  subject  hereto upon  surrender of this Trust Receipt and
Initial  Certification  at  its  office  at  [CUSTODIAN  ADDRESS],  Attention:
Document Custodian.

            Capitalized  terms used herein shall have the meaning  ascribed to
them in the Custodial Agreement.

                                    [_______________________________],
                                       as Custodian

                                    By: ______________________________
                                         Name:
                                         Title:

--------------------------------------------------------------------------------

                                 EXHIBIT I-2

              FORM OF TRUST RECEIPT AND SUBSEQUENT CERTIFICATION

                          [_________________, 200_]

HSBC Bank USA, National Association
      as Trustee for the
Adjustable Rate Mortgage Trust 2005-1
Corporate Trust Services/CSFB ARMT 2005-1
452 Fifth Avenue
New York, New York 10018

Wells Fargo Bank, N.A.,
as Trust Administrator and Master Servicer for the
Adjustable Rate Mortgage Trust 2004-2
9062 Old Annapolis Road,
Columbia, MD 21045

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue
New York, New York 10010
Attention: Peter Sack

      Re:   Custodial Agreement,  dated as of January 1, 2005, among HSBC Bank
            USA, National Association,  as Trustee, Wells Fargo Bank, N.A., as
            Trust Administrator, and [_______________], as Custodian.

        Ladies and Gentlemen:

            In   accordance   with  the   provisions   of  Section  4  of  the
above-referenced  Custodial  Agreement,  the  undersigned,  as the  Custodian,
hereby certifies as to each Subsequent  Mortgage Loan that (i) it has received
the original  Mortgage  Note and  Assignment  of Mortgage with respect to each
such  Subsequent  Mortgage  Loan  identified  on the  Mortgage  Loan  Schedule
attached  hereto  and (ii)  such  Mortgage  Note has been  reviewed  by it and
appears  regular on its face and  relates to such  Subsequent  Mortgage  Loan.
The  Custodian  makes no  representations  as to (i) the  validity,  legality,
enforceability,  sufficiency,  due  authorization or genuineness of any of the
documents  contained  in  each  Custodial  File  or of any  of the  Subsequent
Mortgage  Loans or (ii) the  collectability,  insurability,  effectiveness  or
suitability of any such Subsequent Mortgage Loan.

            The  Custodian  hereby  confirms  that  it is  holding  each  such
Mortgage  Note,  Assignment  of Mortgage and  Assignment  of Note as agent and
bailee of, and custodian  for the  exclusive  use and benefit,  and subject to
the sole  direction,  of the Trustee  pursuant to the terms and  conditions of
the Custodial Agreement.

            This Trust Receipt and Subsequent  Certification  is not divisible
or negotiable.

            The Custodian will accept and act on instructions  with respect to
the  Subsequent  Mortgage  Loans subject  hereto upon  surrender of this Trust
Receipt and  Subsequent  Certification  at its office at [CUSTODIAN  ADDRESS],
Attention:  Document Custodian.

            Capitalized  terms used herein shall have the meaning  ascribed to
them in the Custodial Agreement.

                                    [_______________________________],
                                       as Custodian

                                    By: ______________________________
                                         Name:
                                         Title:

--------------------------------------------------------------------------------

                                  EXHIBIT J

                FORM OF TRUST RECEIPT AND FINAL CERTIFICATION

                                    [date]

HSBC Bank USA, National Association
      as Trustee for the
Adjustable Rate Mortgage Trust 2005-1
Corporate Trust Services/CSFB ARMT 2005-1
452 Fifth Avenue
New York, New York 10018

Wells Fargo Bank, N.A.,
as Trust Administrator and Master Servicer for the
Adjustable Rate Mortgage Trust 2005-1
9062 Old Annapolis Road,
Columbia, MD 21045

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue
New York, New York 10010
Attention: Peter Sack

      Re:   Custodial Agreement,  dated as of January 1, 2005, among HSBC Bank
            USA, National Association,  as Trustee, Wells Fargo Bank, N.A., as
            Trust Administrator, and [____________________], as Custodian

    Ladies and Gentlemen:

            In  accordance  with  the  provisions  of  Section [5][6]  of  the
above-referenced  Custodial  Agreement,  the  undersigned,  as the  Custodian,
hereby  certifies  that as to each  Mortgage  Loan listed on the Mortgage Loan
Schedule  (other  than any  Mortgage  Loan paid in full or any  Mortgage  Loan
listed on the attachment  hereto) it has reviewed the Custodial  Files and has
determined  that (i) all documents  required to be delivered to it pursuant to
Sections 2(i)-(ix)  of the  Custodial  Agreement are in its  possession;  (ii)
such  documents  have been reviewed by it and appear regular on their face and
related  to  such  Mortgage  Loan;   (iii)  all  Assignments  of  Mortgage  or
intervening  assignments of mortgage,  as applicable,  have been submitted for
recording in the jurisdictions in which recording is necessary;  and (iv) each
Mortgage Note has been endorsed as provided in  Section 2(ii) of the Custodial
Agreement   and  each   Mortgage  has  been   assigned  in   accordance   with
Section 2(vi)   of  the   Custodial   Agreement.   The   Custodian   makes  no
representations   as  to   (i)   the   validity,   legality,   enforceability,
sufficiency,  due  authorization  or  genuineness  of  any  of  the  documents
contained in each  Custodial  File or of any of the Mortgage Loans or (ii) the
collectability,   insurability,  effectiveness  or  suitability  of  any  such
Mortgage Loan.

            The  Custodian  hereby  confirms  that  it is  holding  each  such
Custodial  File as agent and bailee of, and  custodian  for the  exclusive use
and benefit,  and subject to the sole  direction,  of Trustee  pursuant to the
terms and conditions of the Custodial Agreement.

            This Trust  Receipt and Final  Certification  is not  divisible or
negotiable.

            The Custodian will accept and act on instructions  with respect to
the Mortgage  Loans  subject  hereto upon  surrender of this Trust Receipt and
Initial  Certification  at  its  office  at  [CUSTODIAN  ADDRESS],  Attention:
Document Custodian.

            Capitalized  terms used herein shall have the meaning  ascribed to
them in the Custodial Agreement.

                                    [_______________________________],
                                       as Custodian

                                    By:______________________________
                                          Name:
                                          Title:

--------------------------------------------------------------------------------

                                  EXHIBIT K

                         FORM OF REQUEST FOR RELEASE

                                    [date]

To:  HSBC Bank USA, National Association

            In connection with the  administration  of the Mortgage Loans held
by you as  Trustee  under the  Pooling  and  Servicing  Agreement  dated as of
January 1, 2005, among Credit Suisse First Boston Mortgage  Securities  Corp.,
as  depositor,  DLJ  Mortgage  Capital,  Inc.,  as  seller,  Select  Portfolio
Servicing,  Inc.,  as a  servicer,  Wilshire  Credit  Corporation,  as special
servicer,  HSBC Bank USA,  National  Association  as trustee,  and Wells Fargo
Bank,  N.A., as a servicer,  master  servicer,  trust  administrator,  and the
other  servicers  that are  signatories  thereto (the  "Pooling and  Servicing
Agreement"),  the  undersigned  hereby requests a release of the Mortgage File
held by you as Trustee with respect to the following  described  Mortgage Loan
for the reason indicated below.

Mortgagor's Name:

Address:

Loan No.:

Reason for requesting file:

____     1.    Mortgage Loan paid in full.
               (The Servicer hereby certifies that all amounts received in
               connection with the Mortgage Loan have been or will be credited
               to the Certificate Account pursuant to the Pooling and Servicing
               Agreement.)

____     2.    Mortgage Loan repurchased.(The Servicer hereby certifies that
               the Purchase Price has been credited to the Certificate Account
               pursuant to the Pooling and Servicing Agreement.)

____     3.    The Mortgage Loan is being foreclosed.

____     4.    Other.  (Describe)
            The undersigned  acknowledges that the above Mortgage File will be
held by the  undersigned in accordance  with the provisions of the Pooling and
Servicing  Agreement  and will be returned,  except if the  Mortgage  Loan has
been paid in full or  repurchased  (in which  case the  Mortgage  File will be
retained by us permanently) when no longer required by us for such purpose.

--------------------------------------------------------------------------------

            Capitalized  terms used herein shall have the meanings ascribed to
them in the Pooling and Servicing Agreement.

                                    [NAME OF SERVICER]

                                    By:_______________________________________
                                          Name:
                                          Title:

--------------------------------------------------------------------------------

                                  EXHIBIT L

                        FORM OF TRANSFEROR CERTIFICATE
                                    [date]

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue, 4th Floor
New York, NY 10010
Attention: John P. Graham

[Trust Administrator]

            Re:   [__________________] Mortgage-Backed Pass-Through
                  Certificates, Series 200_-__
Ladies and Gentlemen:

            In connection  with our  disposition of the above  Certificates we
certify that (a) we understand that the Certificates  have not been registered
under the  Securities  Act of 1933,  as  amended  (the  "Act"),  and are being
disposed  by  us  in a  transaction  that  is  exempt  from  the  registration
requirements of the Act, (b) we have not offered or sold any  Certificates to,
or solicited  offers to buy any  Certificates  from, any person,  or otherwise
approached or  negotiated  with any person with respect  thereto,  in a manner
that would be  deemed,  or taken any other  action  which  would  result in, a
violation of Section 5 of the Act and (c) to the extent we are  disposing of a
Class AR  Certificate,  we have no knowledge the Transferee is not a Permitted
Transferee.

                                    Very truly yours,

                                    __________________________________________
                                    Print Name of Transferor

                                    By:_______________________________________
                                          Authorized Officer

--------------------------------------------------------------------------------

                                 EXHIBIT M-1

                          FORM OF INVESTMENT LETTER
                                    [date]

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue, 4th Floor
New York, NY 10010
Attention: John P. Graham

[Trust Administrator]

            Re:   [__________________] Mortgage-Backed Pass-Through
                  Certificates, Series 200_-__

Ladies and Gentlemen:

            In connection  with our  acquisition of the above  Certificates we
certify that (a) we understand that the  Certificates are not being registered
under  the  Securities  Act of 1933,  as  amended  (the  "Act"),  or any state
securities  laws and are  being  transferred  to us in a  transaction  that is
exempt from the  registration  requirements  of the Act and any such laws, (b)
we are an  "accredited  investor,"  as defined in  Regulation D under the Act,
and have such knowledge and experience in financial and business  matters that
we are  capable  of  evaluating  the merits  and risks of  investments  in the
Certificates,  (c) we have had the opportunity to ask questions of and receive
answers from the Depositor  concerning  the purchase of the  Certificates  and
all matters  relating thereto or any additional  information  deemed necessary
to our  decision to purchase  the  Certificates,  (d) either (i) we are not an
employee  benefit  plan  or  arrangement  that  is  subject  to  the  Employee
Retirement  Income  Security Act of 1974, as amended,  or  Section 4975 of the
Internal Revenue Code of 1986, as amended,  nor are we using the assets of any
such plan or  arrangement,  (ii) we are  providing an Opinion of Counsel which
establishes to the reasonable  satisfaction  of the Trust  Administrator  that
the purchase and holding of ERISA-Restricted  Certificates by, on behalf of or
with "plan assets" of such plan or  arrangement  will not result in non-exempt
prohibited  transactions  under  Section 406 of ERISA or  Section 4975  of the
Code,   and  will  not  subject  the   Depositor,   the  Trustee,   the  Trust
Administrator,  the Master Servicer or any other Servicer to any obligation in
addition to those  undertaken  in this  Agreement  or (iii) if, in the case of
ERISA-Restricted   Certificates   that   have   been   the   subject   of   an
ERISA-Qualifying  Underwriting, we are an insurance company, we are purchasing
such  Certificates  with funds  contained  in an  "insurance  company  general
account" (as such term is defined in  Section V(e)  of Prohibited  Transaction
Class  Exemption  95-60  ("PTCE  95-60")) and our purchase and holding of such
Certificates  are covered under  Sections I and III of PTCE 95-60,  (e) we are
acquiring the  Certificates  for investment for our own account and not with a
view to any distribution of such  Certificates  (but without  prejudice to our
right  at all  times  to sell or  otherwise  dispose  of the  Certificates  in
accordance  with  clause  (g)  below),  (f) we have  not  offered  or sold any
Certificates  to,  or  solicited  offers  to buy any  Certificates  from,  any
person,  or otherwise  approached or  negotiated  with any person with respect
thereto,  or taken any other  action  which  would  result in a  violation  of
Section 5 of the Act, and (g) we will not sell,  transfer or otherwise dispose
of any  Certificates  unless (1) such sale,  transfer or other  disposition is
made  pursuant  to an  effective  registration  statement  under the Act or is
exempt from such registration  requirements,  and if requested, we will at our
expense  provide an opinion of counsel  satisfactory to the addressees of this
Certificate  that  such  sale,  transfer  or  other  disposition  may be  made
pursuant to an exemption  from the Act, (2) the  purchaser  or  transferee  of
such   Certificate  has  executed  and  delivered  to  you  a  certificate  to
substantially  the same effect as this  certificate,  and (3) the purchaser or
transferee  has otherwise  complied with any conditions for transfer set forth
in the Pooling and Servicing Agreement.

                                    Very truly yours,

                                    __________________________________________
                                    Print Name of Transferor

                                    By:_______________________________________
                                          Authorized Officer

--------------------------------------------------------------------------------

                                 EXHIBIT M-2

                           FORM OF RULE 144A LETTER
                                    [date]

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue, 4th Floor
New York, NY 10010
Attention: John P. Graham

[Trust Administrator]

            Re:   [__________________] Mortgage-Backed Pass-Through
                  Certificates, Series 200_-__

Ladies and Gentlemen:

            In connection  with our  acquisition of the above  Certificates we
certify that (a) we understand that the  Certificates are not being registered
under  the  Securities  Act of 1933,  as  amended  (the  "Act"),  or any state
securities  laws and are  being  transferred  to us in a  transaction  that is
exempt from the  registration  requirements  of the Act and any such laws, (b)
we have such knowledge and  experience in financial and business  matters that
we are  capable  of  evaluating  the merits  and risks of  investments  in the
Certificates,  (c) we have had the opportunity to ask questions of and receive
answers from the Depositor  concerning  the purchase of the  Certificates  and
all matters  relating thereto or any additional  information  deemed necessary
to our  decision to purchase  the  Certificates,  (d) either (i) we are not an
employee  benefit  plan  or  arrangement  that  is  subject  to  the  Employee
Retirement  Income  Security Act of 1974, as amended,  or  Section 4975 of the
Internal Revenue Code of 1986, as amended,  nor are we using the assets of any
such plan or  arrangement,  (ii) we are  providing an Opinion of Counsel which
establishes to the reasonable  satisfaction  of the Trust  Administrator  that
the purchase and holding of ERISA-Restricted  Certificates by, on behalf of or
with "plan  assets" of such plan will not  result in a  non-exempt  prohibited
transaction  under  Section 406 of ERISA or Section 4975 of the Code, and will
not subject the Depositor,  the Trustee, the Trust  Administrator,  the Master
Servicer  or any  other  Servicer  to any  obligation  in  addition  to  those
undertaken in this  Agreement or (iii) if, in the case of an  ERISA-Restricted
Certificates that have been the subject of an  ERISA-Qualifying  Underwriting,
we are an insurance  company,  we are purchasing such  Certificates with funds
contained in an "insurance  company general  account" (as such term is defined
in  Section V(e)  of  Prohibited  Transaction  Class  Exemption  95-60  ("PTCE
95-60")) and our purchase and holding of such  Certificates  are covered under
Sections I and III of PTCE 95-60,  (e) we have not,  nor has anyone  acting on
our behalf offered,  transferred,  pledged,  sold or otherwise disposed of the
Certificates,  any interest in the  Certificates or any other similar security
to,  or  solicited  any  offer to buy or  accept a  transfer,  pledge or other
disposition  of the  Certificates,  any  interest in the  Certificates  or any
other  similar  security  from, or otherwise  approached  or  negotiated  with
respect to the  Certificates,  any interest in the  Certificates  or any other
similar  security  with,  any  person  in any  manner,  or  made  any  general
solicitation by means of general  advertising or in any other manner, or taken
any other action,  that would  constitute a distribution  of the  Certificates
under the Act or that  would  render the  disposition  of the  Certificates  a
violation of Section 5 of the Act or require  registration  pursuant  thereto,
nor will act, nor has  authorized or will authorize any person to act, in such
manner  with   respect  to  the   Certificates,   (f)  we  are  a   "qualified
institutional  buyer"  as that  term is  defined  in Rule  144A  under the Act
("Rule 144A") and have completed  either of the forms of certification to that
effect  attached  hereto as Annex 1 or Annex 2, (g) we are aware that the sale
to us is being made in reliance  on Rule 144A,  and (i) we are  acquiring  the
Certificates  for our own  account  or for  resale  pursuant  to Rule 144A and
further,   understand  that  such  Certificates  may  be  resold,  pledged  or
transferred  only  (A)  to a  person  reasonably  believed  to be a  qualified
institutional  buyer that  purchases for its own account or for the account of
a  qualified  institutional  buyer to whom  notice is given  that the  resale,
pledge or transfer is being made in reliance on Rule 144A,  or (B) pursuant to
another exemption from registration under the Act.

                                    Very truly yours,

                                    __________________________________________
                                    Print Name of Transferor

                                    By:_______________________________________
                                          Authorized Officer

--------------------------------------------------------------------------------

                                  EXHIBIT N

              FORM OF INVESTOR TRANSFER AFFIDAVIT AND AGREEMENT

STATE OF          )
                        : ss.:
COUNTY OF         )

            [NAME OF OFFICER], being first duly sworn, deposes and says:

            1.    That he is [Title of Officer] or [Name of Owner]  (record or
beneficial  owner  (the  "Owner")  of the Class  [AR/AR-L]  Certificates  (the
"Class [AR/AR-L]  Certificates")),  a [savings institution] [corporation] duly
organized   and   existing   under   the   laws  of  [the   State  of  ]  [the
United States], on behalf of which he makes this affidavit and agreement.

            2.    That the  Owner  (i) is not and will not be a  "disqualified
organization"   as   of   [date   of   transfer]   within   the   meaning   of
Section 860E(e)(5)  of the  Internal  Revenue  Code of 1986,  as amended  (the
"Code"),  (ii) will endeavor to remain other than a disqualified  organization
for so long as it  retains  its  ownership  interest  in the  Class  [AR/AR-L]
Certificates,  and (iii) is acquiring the Class [AR/AR-L] Certificates for its
own   account.   A  "Permitted   Transferee"   is  any  person  other  than  a
"disqualified    organization."    (For   this   purpose,    a   "disqualified
organization"  means the United  States,  any state or  political  subdivision
thereof,  any agency or instrumentality of any of the foregoing (other than an
instrumentality  all of the activities of which are subject to tax and, except
for the Federal Home Loan Mortgage  Corporation,  a majority of whose board of
directors  is not  selected  by any such  governmental  entity) or any foreign
government,  international  organization or any agency or  instrumentality  of
such  foreign  government  or  organization,  any rural  electric or telephone
cooperative,  or any organization  (other than certain farmers'  cooperatives)
that is generally  exempt from federal income tax unless such  organization is
subject to the tax on unrelated business taxable income).

            3.    That  the  Owner  is  aware  (i) of the tax  that  would  be
imposed  on  transfers  of  Class   [AR/AR-L]   Certificates  to  disqualified
organizations  under the Code;  (ii) that such tax would be on the transferor,
or, if such  transfer  is through an agent  (which  person  includes a broker,
nominee or middleman)  for a  non-Permitted  Transferee,  on the agent;  (iii)
that the person  otherwise  liable for the tax shall be relieved of  liability
for the tax if the  transferee  furnishes to such person an affidavit that the
transferee  is a  Permitted  Transferee  and,  at the time of  transfer,  such
person does not have actual  knowledge  that the affidavit is false;  and (iv)
that the Class [AR/AR-L]  Certificates may be "noneconomic residual interests"
within the meaning of Treasury  regulations  promulgated  pursuant to the Code
and that the transferor of a noneconomic  residual interest will remain liable
for any taxes due with respect to the income on such residual  interest,  if a
significant  purpose of the  transfer was to enable the  transferor  to impede
the assessment or collection of tax.

            4.    That  the   Owner  is  aware  of  the  tax   imposed   on  a
"pass-through  entity"  holding Class  [AR/AR-L]  Certificates  if at any time
during the taxable year of the pass-through entity a non-Permitted  Transferee
is the record  holder of an  interest in such  entity.  (For this  purpose,  a
"pass through entity" includes a regulated  investment  company, a real estate
investment  trust or common trust fund, a  partnership,  trust or estate,  and
certain cooperatives.)

            5.    That the Owner is aware that the Trustee  will not  register
the Transfer of any Class [AR/AR-L]  Certificates  unless the  transferee,  or
the  transferee's  agent,  delivers to it an affidavit  and  agreement,  among
other  things,   in  substantially   the  same  form  as  this  affidavit  and
agreement.  The Owner  expressly  agrees that it will not  consummate any such
transfer if it knows or believes that any of the representations  contained in
such affidavit and agreement are false.

            6.    That the Owner has  reviewed the  restrictions  set forth on
the  face  of  the  Class  [AR/AR-L]   Certificates   and  the  provisions  of
Section 6.02  of the Pooling  and  Servicing  Agreement  under which the Class
[AR/AR-L]  Certificates  were issued.  The Owner expressly  agrees to be bound
by and to comply with such restrictions and provisions.

            7.    That the Owner  consents to any additional  restrictions  or
arrangements  that  shall be  deemed  necessary  upon  advice  of  counsel  to
constitute  a  reasonable  arrangement  to  ensure  that the  Class  [AR/AR-L]
Certificates will only be owned,  directly or indirectly,  by an Owner that is
a Permitted Transferee.

            8.    That  the   Owner's   Taxpayer   Identification   Number  is
________________.

            9.    That the  Owner  is a  citizen  or  resident  of the  United
States,  a  corporation,  partnership or other entity created or organized in,
or under the laws of, the United States,  any State thereof or the District of
Columbia,  or an estate or trust whose income from sources  without the United
States is  includable  in gross income for United  States  federal  income tax
purposes  regardless of its connection with the conduct of a trade or business
within the United States.

            10.   That no purpose of the Owner  relating  to the  purchase  of
the Class  [AR/AR-L]  Certificate  by the  Owner is or will be to  impede  the
assessment or collection of tax.

            11.   That the Owner has no present  knowledge or expectation that
it will be unable to pay any United  States taxes owed by it so long as any of
the Certificates remain outstanding.

            12.   That the Owner has no present  knowledge or expectation that
it will become insolvent or subject to a bankruptcy  proceeding for so long as
any of the Certificates remain outstanding.

            13.   That no  purpose  of the Owner  relating  to any sale of the
Class  [AR/AR-L]  Certificate by the Owner will be to impede the assessment or
collection of tax.

            14.   The Owner hereby  agrees to  cooperate  with the Trustee and
to  take  any  action  required  of it by the  Code  or  Treasury  regulations
thereunder  (whether  now or  hereafter  promulgated)  in order to  create  or
maintain the REMIC status of the Trust Fund.

            15.   That the  Owner is not an  employee  benefit  or other  plan
subject to the prohibited  transaction  provisions of the Employee  Retirement
Income  Security Act of 1974, as amended  ("ERISA"),  or  Section 4975  of the
Internal  Revenue Code of 1986,  as amended  (the  "Code") (a "Plan"),  or any
other person (including an investment  manager, a named fiduciary or a trustee
of any Plan) acting,  directly or  indirectly,  on behalf of or purchasing any
Certificate with "plan assets" of any Plan.

            16.   The Owner  hereby  agrees  that it will not take any  action
that  could  endanger  the REMIC  status  of the  Trust  Fund or result in the
imposition of tax on the Trust Fund unless  counsel for, or acceptable to, the
Trustee has  provided an opinion  that such action will not result in the loss
of such REMIC status or the imposition of such tax, as applicable.

            17.   The  Owner  has  provided  financial   statements  or  other
financial  information  requested by the  transferor  in  connection  with the
transfer of the Residual  Certificates  to permit the transferor to assess the
financial capability of the Owner to pay any such taxes.

            IN WITNESS  WHEREOF,  the Owner has caused this  instrument  to be
executed on its behalf,  pursuant to the  authority of its Board of Directors,
by its [Title of Officer]  and its  corporate  seal to be  hereunto  attached,
attested by its [Assistant] Secretary, this ____ day of ___________.

                                    [NAME OF OWNER]

                                    By:   ___________________________________
                                          [Name of Officer]
                                          [Title of Officer]

[Corporate Seal]

ATTEST:

____________________________________
[Assistant] Secretary

--------------------------------------------------------------------------------

            Personally  appeared before me the above-named  [Name of Officer],
known or  proved  to me to be the  same  person  who  executed  the  foregoing
instrument and to be the [Title of Officer] of the Owner,  and acknowledged to
me that he  executed  the  same as his  free act and deed and the free act and
deed of the Owner.

Subscribed and sworn before me this _____ day of _______________________.

                                    __________________________________________
                                    NOTARY PUBLIC

                                    COUNTY OF ________________________________

                                    STATE OF _________________________________

                                    My Commission expires the _____ day of
                                    __________________, 20____.

--------------------------------------------------------------------------------

                                  EXHIBIT O

                         FORM OF TRANSFER CERTIFICATE

                                    [date]

Credit Suisse First Boston Mortgage Securities Corp.
11 Madison Avenue, 4th Floor
New York, New York 10010
Attention:  John P. Graham

[_____________________]
[_____________________]
[_____________________]

            Re:   [_________________________] Mortgage Backed Pass Through
                  Certificates, Series 200_ ___, Class AR (the "Certificates")

Ladies and Gentlemen:

            This letter is  delivered  to you in  connection  with the sale by
_________________ (the "Seller") to ____________________________________  (the
"Purchaser")  of a  _______%  Percentage  Interest  in  the  above  referenced
Certificates,  pursuant to Section 6.02 of the Pooling and Servicing Agreement
dated as of  January  1, 2005,  among  Credit  Suisse  First  Boston  Mortgage
Securities Corp., as Depositor,  DLJ Mortgage Capital, Inc., as seller, Select
Portfolio  Servicing,  Inc., as a servicer,  Wilshire Credit  Corporation,  as
special servicer,  HSBC Bank USA, National Association as trustee, Wells Fargo
Bank, N.A., as a servicer,  master servicer and trust  administrator,  and the
other  servicers  that are  signatories  thereto (the  "Pooling and  Servicing
Agreement").  All terms used herein and not  otherwise  defined shall have the
meanings set forth in the Pooling and Servicing  Agreement.  The Seller hereby
certifies,  represents and warrants to, and covenants  with, the Depositor and
the Trustee that:

            1.    No  purpose  of  the   Seller   relating   to  sale  of  the
Certificate  by the Seller to the Purchaser is or will be to enable the Seller
to impede the assessment or collection of any tax.

            2.    The Seller  understands  that the Purchaser has delivered to
the Trustee a transfer  affidavit  and  agreement in the form  attached to the
Pooling  and  Servicing  Agreement  as Exhibit N. The Seller  does not know or
believe that any representation contained therein is false.

            3.    The  Seller  has  no  actual  knowledge  that  the  proposed
Transferee is not a Permitted Transferee.

            4.    The Seller has no actual  knowledge that the Purchaser would
be  unwilling  or unable to pay taxes due on its share of the  taxable  income
attributable to the Certificate.

            5.    The Seller has conducted a reasonable  investigation  of the
financial  condition of the Purchaser  and, as a result of the  investigation,
found that the  Purchaser  has  historically  paid its debts as they came due,
and found no  significant  evidence to indicate  that the  Purchaser  will not
continue to pay its debts as they come due in the future.

            6.    The  Purchaser  has  represented  to the Seller that, if the
Certificate  constitutes a noneconomic  residual interest,  it (i) understands
that  as  holder  of  a  noneconomic   residual  interest  it  may  incur  tax
liabilities  in excess of any cash flows  generated by the interest,  and (ii)
intends to pay taxes  associated  with its holding of the  Certificate as they
become due.

                                    Very truly yours,

                                    [SELLER]

                                    By:   ____________________________________
                                          Name:
                                          Title:

--------------------------------------------------------------------------------

                                  EXHIBIT P

                      FORM OF SPS MORTGAGE LOANS REPORT

         DATA AND FORMAT TO BE PROVIDED BY SPS TO THE MASTER SERVICER
                              (in Excel format)

                            ALL SPS MORTGAGE LOANS

FIELD FORMAT                                                  FIELD
Name*                                                         Text
Lien Position *                                               Text/Number
FICO Score*                                                   Number
Original Occupancy*                                           Text
Documentation*                                                Text
Purpose*                                                      Text
Original Loan Amount*                                         Number
Original Appraisal Value*                                     Number
Original LTV*                                                 Number
Original P&I*                                                 Number
Original Interest Rate*                                       Number
First Payment Date*                                           MM/DD/YY
Origination Date*                                             MM/DD/YY
Originator*                                                   Text
Loan Term*                                                    Number
Product Type (adjustable rate or fixed rate)*                 Text
Property Type*                                                Text
Street Address*                                               Text
City*                                                         Text
Zip Code*                                                     Text
State*                                                        Text
MI Certificate Number*                                        Number
Prepayment Flag                                               Text
Prepayment Expiration Date                                    MM/DD/YY
Loan Number                                                   Text
Deal Identifier by Loan                                       Text
Current Loan Amount                                           Number
Current LTV                                                   Number
Current Interest Rate                                         Number
Last Interest Payment Date                                    MM/DD/YY
Current P&I Payment Amount                                    Number
Paid Off Code                                                 Text
Scheduled Balance                                             Number
Calculation of Retained Yield by Loan Number (if applicable
       to the transaction)                                      Number
Reporting of Delinquency Status on Defaulted Mortgage Loans   Text
Current Market Value                                          Number
Date of Market Value                                          MM/DD/YY
As-is Value                                                   Number
Repaired Value                                                Number
Type of Valuation                                             Text
Foreclosure Flag                                              Text
Bankruptcy Flag                                               Text
Date NOD sent to MI company                                   MM/DD/YY
Foreclosure Start Date (Referral Date)                        MM/DD/YY
Scheduled Foreclosure Sale Date                               MM/DD/YY
Foreclosure Actual Sale Date                                  MM/DD/YY
Actual Notice of Intent Date                                  MM/DD/YY
Actual First Legal Date                                       MM/DD/YY
Bankruptcy Chapter                                            Number
Actual Bankruptcy Start Date                                  MM/DD/YY
Actual Payment Plan Start and End Dates                       MM/DD/YY
List Date                                                     MM/DD/YY
List Price                                                    Number
Vacancy/Occupancy Status                                      Text
Actual Eviction Start Date                                    MM/DD/YY
Actual Eviction Completion Date                               MM/DD/YY
Actual REO Start Date                                         MM/DD/YY
Sales Price                                                   Number
Actual Closing Date                                           MM/DD/YY
Net Sales Proceeds                                            Number
Mortgage Insurance Claim Filing Date                          MM/DD/YY
Mortgage Insurance Proceeds Received                          Number
Date Mortgage Insurance Proceeds Received                     MM/DD/YY
Collection History

--------------------------------------------------------------------------------

                                  EXHIBIT Q

                   FORM OF FORECLOSURE SETTLEMENT STATEMENT

REMIC #                                                     Ending Interest
                                                            Rate:
Original Amount of Loan:                                    Fixed or
                                                            Adjustable:
UPB Accrued Int to frcl sale:
Advanced Delinquent Interest:
Date Borrower Paid To:        /  /
Borrower's Name:
Property Address:

MSP Bank/Category
Note Date:                    /  /
Date of REO:                  /  /
Disposition Date:             /  /

                              Amount      Date of Valuation Type of Valuation
Market Value       AS IS:                        / /
                   Repaired
Supplemental Value AS IS:                        / /
                   Repaired
REO BPO Value:                                   / /
List Price:
Sales Price:

                   Proceeds               Expenses*
List Price:                               Servicing Advances:

                                          Sales Price:                  0.00                                  Payee 70R01
                                                                   Acquisition:
Broker's                                                       Payee 75R60 REO:
Commission:
Bonus Commission:                                                   Payee 75R49
                                                                   Foreclosure:
Lien Purchase/Paid                                          Payee 75R36 Escrow:
Off:
Seller Closing                                                      Payee 75R52
Costs:                                                              Bankruptcy:
Repair Costs:                                               Discrepancy Amount:
Seller Concessions:                                           Servicing Advance  0.00
                                                                         Total:
Other Closing Costs:                      Advances Applied After Liquidation:
                                          Prior Additional Advances:
Net Proceeds:                 0.00        Escrow Advance:
                                          Interest on Advances:
Escrow Balance:                           Other Advances:
Suspense Balance:                         Servicing Advance Holdbacks:
Restricted Escrow:                                         Property Inspection:
Rental Income                                                              BPO:
Received:
Insurance Settlement                                              Lender Placed
Received:                                                            Insurance:
Other:                                                               Utilities:
                                                              REO Repair Costs:
Total Liquidation Proceeds:   0.00                            Foreclosure Fees:
Total Liquidation Expenses:   0.00                                  Bankruptcy:
Net Liquidation Proceeds:     0.00                              Eviction Costs:
Loan Principal Balance:                                           Transfer Tax:
Realized Gain/Loss Amount:    0.00                           Reconveyance Fees:
Additional Proceeds Applied:                                        Demand Fee:
Prior Additional Proceeds:                                     Total Holdbacks:  0.00
Loss Severity:                #DIV/0!                     Other Fees (Including
                                                                   Fee Code B):
Notes:                                                  UPB Accrued Interest to   0.00
                                                                           COE:
                                                            Advanced Delinquent   0.00
                                                                      Interest:
                                                             Stopped Delinquent
                                                                      Interest:
                                                             Deferred Interest:
                                                           Additional Interest:
                                                    Total Liquidation Expenses:   0.00

                                                                      ____________________________________________
*All amounts will be itemized, and to the extent not itemized, this form will
be accompanied by documentation supporting all amounts claimed on this form.

--------------------------------------------------------------------------------

                                  EXHIBIT R

                    FORM OF SUBSEQUENT TRANSFER AGREEMENT

            THIS SUBSEQUENT TRANSFER AGREEMENT,  dated as of [______________],
2004 (this "Subsequent Transfer Agreement"),  among CREDIT SUISSE FIRST BOSTON
MORTGAGE  SECURITIES  CORP.,  a  Delaware   corporation,   as  depositor  (the
"Depositor"),  DLJ  MORTGAGE  CAPITAL,  INC., a Delaware  corporation,  in its
capacity  as seller  under the  Pooling and  Servicing  Agreement  referred to
below (the "Seller"), HSBC BANK USA, NATIONAL ASSOCIATION,  a national banking
association,  as  trustee  (the  "Trustee")  and WELLS  FARGO  BANK,  N.A.,  a
national   banking   association,   as   trust   administrator   (the   "Trust
Administrator");

            WHEREAS,  the  parties  hereto are also  among the  parties to the
pooling and  servicing  agreement  (the  "Agreement"),  dated as of January 1,
2005,  among the  Depositor,  the Trustee,  Wells Fargo Bank,  N.A.,  as trust
administrator,  master servicer, a servicer and back-up servicer, DLJ Mortgage
Capital,  Inc., as seller ("DLJMC"),  Select Portfolio  Servicing,  Inc., as a
servicer,  Wilshire Credit  Corporation,  as special  servicer,  and the other
servicers   that  are   signatories   thereto  (the   "Pooling  and  Servicing
Agreement"),   in  relation  to  the  Credit  Suisse  First  Boston   Mortgage
Securities  Corp.,  Adjustable  Rate  Mortgage  Trust 2005-1  Adjustable  Rate
Mortgage-Backed Pass-Through Certificates, Series 2005-1;

            WHEREAS,  Sections 2.01(f) of the Pooling and Servicing  Agreement
provides  for the  parties  hereto  to enter  into  this  Subsequent  Transfer
Agreement  in  accordance  with the terms and  conditions  of the  Pooling and
Servicing Agreement;

            NOW,  THEREFORE,  in  consideration  of the premises and for other
good and valuable  consideration  the receipt and adequacy of which are hereby
acknowledged the parties hereto agree as follows:

            (i)   The  "Subsequent  Transfer  Date"  and  "Subsequent  Cut-off
Date"  with  respect  to  this   Subsequent   Transfer   Agreement   shall  be
[_________], 2005 and [_____] 1, 2005, respectively.

            (ii)  The "Aggregate  Subsequent  Purchase Amount" with respect to
this  Subsequent  Transfer  Agreement  shall be  $[______________],  provided,
however,  that such  amount  shall not  exceed  the  amount on  deposit in the
Prefunding Account.

            (iii) The  Subsequent  Mortgage  Loans  conveyed on the Subsequent
Transfer  Date  shall  satisfy  the pool  characteristics  for the Trust  Fund
identified in Section 2.01(f) of the Pooling and Servicing Agreement.

            (iv)  In case any provision of this Subsequent  Transfer Agreement
shall be  invalid,  illegal  or  unenforceable,  the  validity,  legality  and
enforceability  of the remaining  provisions or  obligations  shall not in any
way be affected or impaired thereby.

            (v)   In the event of any conflict  between the provisions of this
Subsequent  Transfer  Agreement and the Pooling and Servicing  Agreement,  the
provisions of the Pooling and Servicing  Agreement shall prevail.  Capitalized
terms used herein and not  otherwise  defined have the meanings in the Pooling
and Servicing Agreement.

            (vi)  The Seller hereby sells,  transfers,  assigns, sets over and
otherwise  conveys to the  Depositor,  without  recourse,  all right title and
interest in the Subsequent  Mortgage Loans identified in Schedule A, including
all interest and principal due on or with respect to such Subsequent  Mortgage
Loans on or after the  Subsequent  Cut-off Date and all interest and principal
payments on such  Subsequent  Mortgage  Loans received prior to the Subsequent
Cut-off  Date in  respect  of  installments  of  interest  and  principal  due
thereafter,  but not including  principal and interest due on such  Subsequent
Mortgage  Loans prior to the Subsequent  Cut-off Date, any insurance  policies
in respect of such  Subsequent  Mortgage  Loans and all proceeds of any of the
foregoing.

            (vii) This  Subsequent  Transfer  Agreement  shall be governed by,
and shall be construed and enforced in  accordance  with the laws of the State
of New York.

            (viii)      The Subsequent  Transfer  Agreement may be executed in
one or more  counterparts,  each of which so executed and  delivered  shall be
deemed an original,  but all such  counterparts  together shall constitute but
one and the same instrument.

--------------------------------------------------------------------------------

            IN  WITNESS  WHEREOF,  the  parties  to this  Subsequent  Transfer
Agreement  have  caused  their names to be signed  hereto by their  respective
officers thereunto duly authorized as of the day and year first above written.

                                    CREDIT SUISSE FIRST BOSTON MORTGAGE
                                    SECURITIES CORP.,
                                       as Depositor

                                    By:_______________________________________
                                        Name:
                                        Title:

                                    DLJ Mortgage Capital, Inc.,
                                       as Seller

                                    By:_______________________________________
                                        Name:
                                        Title:

                                    HSBC BANK USA,  NATIONAL ASSOCIATION,
                                       not in its individual capacity, but
                                       solely as Trustee

                                    By:_______________________________________
                                        Name:
                                        Title:

                                    WELLS FARGO BANK, N.A.,
                                       not in its individual capacity, but
                                       solely as Trust Administrator

                                    By:_______________________________________
                                        Name:
                                        Title:

--------------------------------------------------------------------------------

Acknowledged and Agreed:

WELLS FARGO BANK, N.A.,
   as Master Servicer

By:_______________________________________
     Name:
     Title:

WELLS FARGO BANK, N.A.,
   as Servicer

By:_______________________________________
     Name:
     Title:

--------------------------------------------------------------------------------

                                  EXHIBIT S

               FORM OF MONTHLY STATEMENT TO CERTIFICATEHOLDERS

(i)   With respect to each Class of Certificates which are not Notional
      Amount Certificates and, unless otherwise stated, the related
      Distribution Date,

      (a)   the Initial Class Principal Balance of such Class as of the
            Cut-off Date;

      (b)   the Class Principal Balance of such Class before giving effect to
            the distribution of principal and interest;

      (c)   the amount of the related distribution on such Class allocable to
            interest;

      (d)   the amount of the related distribution on such Class allocable to
            principal;

      (e)   the sum of the principal and interest payable to such Class;

      (f)   the Realized Loss allocable to such Class;

      (g)   the Class Unpaid Interest Amount allocable to such Class;

      (h)   the Class Principal Balance of such Class after giving effect to
            the distribution of principal and interest;

      (i)   the Pass-Through Rate for such Class;

      (j)   any Basis Risk Shortfall allocable to such Class, if such amount
            is greater than zero;

      (k)   any shortfall in principal allocable to such Class, if such
            amount is greater than zero;

(ii)  with respect to each Class of Certificates which are Notional Amount
      Certificates and, unless otherwise stated, the related Distribution
      Date,

      (a)   the Notional Amount of such Class as of the Cut-off Date;

      (b)   the Notional Amount of such Class before giving effect to the
            distribution of interest;

      (c)   the amount of the related distribution on such Class allocable to
            interest;

      (d)   the amount of the related distribution on such Class allocable to
            principal;

      (e)   the sum of the principal and interest payable to such class;

      (f)   the Realized Loss allocable to such Class;

      (g)   the Class Unpaid Interest Amount allocable to such Class;

      (h)   the Notional Amount of such Class after giving effect to the
            distribution of interest;

      (i)   the Pass-Through Rate for such Class;

      (j)   any Basis Risk Shortfall allocable to such Class, if such amount
            is greater than zero;

(iii) with respect to a $1000 factor of the Initial Class Principal Balance
      of each Class of Certificates which are not Notional Amount
      Certificates and the related Distribution Date,

      (a)   the CUSIP number assigned to such Class;

      (b)   the Class Principal Balance of such Class factor prior to giving
            effect to the distribution of principal and interest;

      (c)   the amount of the related distribution allocable to interest on
            such Class factor;

      (d)   the amount of the related distribution allocable to principal on
            such Class factor;

      (e)   the sum of the principal and interest payable to such Class
            factor;

      (f)   the Class Principal Balance of such Class factor after giving
            effect to the distribution of principal and interest;

(iv)  with respect to a $1000 factor of the Initial Class Principal Balance
      of each Class of Certificates which are Notional Amount Certificates
      and the related Distribution Date,

      (a)   the CUSIP number assigned to such Class;

      (b)   the Notional Amount of such Class factor prior to giving effect
            to the distribution of interest;

      (c)   the amount of the related distribution allocable to interest on
            such Class factor;

      (d)   the amount of the related distribution allocable to principal on
            such Class factor;

      (e)   the sum of the principal and interest payable to such Class
            factor;

      (f)   the Notional Amount of such Class factor after giving effect to
            the distribution of interest;

(v)   with respect to each Loan Group, in the aggregate, and, unless
      otherwise stated, the related Distribution Date,

      (a)   the Scheduled Payment of principal for such Loan Group;

      (b)   the amount of Principal Prepayments allocable to such Loan Group;

      (c)   the amount of principal allocable to such Loan Group as a result
            of repurchased Mortgage Loans in such Loan Group;

      (d)   the Substitution Adjustment Amount allocable to such Loan Group;

      (e)   the amount of Net Liquidation Proceeds allocable to such Loan
            Group;

      (f)   the amount of Insurance Proceeds allocable to such Loan Group;

      (g)   the amount of any other distributions allocable to principal for
            such Loan Group;

      (h)   the number of Mortgage Loans in such Loan Group as of the first
            day of the related Collection Period;

      (i)   the aggregate Stated Principal Balance of the Mortgage Loans in
            such Loan Group as of the first day of the related Collection
            Period;

      (j)   the number of Mortgage Loans in such Loan Group as of the last
            day of the related Collection Period;

      (k)   the aggregate Stated Principal Balance of the Mortgage Loans in
            such Loan Group as of the last day of the related Collection
            Period;

      (l)   the Master Servicing Fee, by Loan Group;

      (m)   the sum of the Servicing Fee, the Mortgage Guaranty Insurance
            Policy fees, if applicable and the [RMIC/TGIC/MGIC] PMI fees, if
            applicable, for such Loan Group;

      (n)   the Trust Administrator Fee applicable to such Loan Group;

      (o)   the amount of current Advances allocable to such Loan Group;

      (p)   the amount of outstanding Advances allocable to such Loan Group;

      (q)   the number and aggregate principal amounts of Mortgage Loans
            delinquent (1) 31 to 60 days, (2) 61 to 90 days and (3) 91 days
            or more, for such Loan Group, including delinquent bankrupt
            Mortgage Loans but excluding foreclosure and REO Mortgage Loans;

      (r)   the number and aggregate principal amounts of Mortgage Loans that
            are currently in bankruptcy, but not delinquent, for such Loan
            Group;

      (s)   the number and aggregate principal amounts of Mortgage Loans that
            are in foreclosure for such Loan Group;

      (t)   the Rolling Three Month Delinquency Rate or Rolling Six Month
            Delinquency Rate for such Loan Group;

      (u)   the number and aggregate principal amount of any REO properties
            as of the close of business on the Determination Date preceding
            such Distribution Date for such Loan Group;

      (v)   current Realized Losses allocable to such Loan Group;

      (w)   cumulative Realized Losses allocable to such Loan Group;

      (x)   the weighted average term to maturity of the Mortgage Loans in
            such Loan Group as of the close of business on the last day of
            the calendar month preceding the related Distribution Date;

      (y)   the number and principal amount of claims submitted under the
            Mortgage Guaranty Insurance Policy, as applicable;

      (z)   the number and principal amount of claims paid under the
            [RMIC/TGIC/MGIC] PMI Policy, as applicable;

      (aa)  the number of Mortgage Loans in such Loan Group that have
            Assigned Prepayment Premiums and for which prepayments were made
            during the related Collection Period, as applicable;

      (bb)  the aggregate principal balance of Mortgage Loans in such Loan
            Group that have Assigned Prepayment Premiums and for which
            prepayments were made during the related Collection Period, as
            applicable;

      (cc)  the aggregate amount of Assigned Prepayment Premiums collected
            for such Loan Group during the related Collection Period, as
            applicable;

      (dd)  current Realized Losses allocated to each Mortgage Loan in such
            Loan Group that has previously been allocated a Realized Loss;

      (ee)  cumulative Realized Losses allocated to each Mortgage Loan in
            such Loan Group that has previously been allocated a Realized
            Loss;

      (ff)  current Recoveries allocable to such Loan Group;

      (gg)  cumulative Recoveries allocable to such Loan Group;

      (hh)  current aggregate Stated Principal Balance of Qualified
            Substitute Mortgage Loans substituted for Deleted Mortgage Loans
            in such Loan Group;

      (ii)  cumulative aggregate Stated Principal Balance of Qualified
            Substitute Mortgage Loans substituted for Deleted Mortgage Loans
            in such Loan Group;

      (jj)  with respect to all of the Mortgage Loans, in the aggregate, and,
            unless otherwise stated, the related Distribution Date, for each
            Servicer that is servicing any of such Mortgage Loans, the
            aggregate Stated Principal Balance of Mortgage Loans being
            serviced by such Servicer as of such Distribution Date; and

      (kk)  [reserved];

(vii) with respect to each overcollateralized Group of Certificates and,
      unless otherwise stated, the related Distribution Date,

      (a)   the Targeted Overcollateralization Amount for such Group;

      (b)   the Overcollateralization Amount for such Group;

      (c)   the Overcollateralization Deficiency for such Group;

      (d)   the Overcollateralization Release Amount for such Group;

      (e)   the Monthly Excess Interest for such Group;

      (f)   the amount of any payment to the [Class __-X] Certificates
            related to such Group;

      (g)   if applicable, the Excess Interest Amount from an unrelated Group
            of Certificates that provides additional credit enhancement to
            the related overcollateralized Group of Certificates.

--------------------------------------------------------------------------------

                                  EXHIBIT T

                       FORM OF DEPOSITOR CERTIFICATION

      Re:   Credit Suisse First Boston Mortgage Securities Corp.,
            Adjustable Rate Mortgage Trust 2005-1,
            Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series
            2005-1

            I, __________________________, certify that:

            1.    I have  reviewed  this annual  report on Form 10-K,  and all
reports on Form 8-K  containing  distribution  and servicing  reports filed in
respect of periods  included  in the year  covered by this annual  report,  of
Adjustable  Rate  Mortgage  Trust  2005-1,   Adjustable  Rate  Mortgage-Backed
Pass-Through Certificates, Series 2005-1 (the "Trust");

            2.    Based on my knowledge,  the  information  in these  reports,
taken as a whole,  does not contain any untrue statement of a material fact or
omit to state a material fact necessary to make the statements  made, in light
of the circumstances  under which such statements were made, not misleading as
of the last day of the period covered by this annual report;

            3.    Based  on  my  knowledge,   the   distribution   information
required to be prepared by the Trust  Administrator  based upon the  servicing
information  required to be provided by each Servicer and the Master  Servicer
under the Pooling and Servicing Agreement is included in these reports;

            4.    Based  on  my  knowledge  and  upon  the  annual  compliance
statements  included in the report and  required to be  delivered to the Trust
Administrator  in  accordance  with the  terms of the  Pooling  and  Servicing
Agreement and based upon the review  required  under the Pooling and Servicing
Agreement,  and except as  disclosed  in the  report,  each  Servicer  and the
Master Servicer has fulfilled its obligations  under the Pooling and Servicing
Agreement; and

            5.    The reports disclose all significant  deficiencies  relating
to each  Servicer's  and the Master  Servicer's  compliance  with the  minimum
servicing  standards  based,  in each  case,  upon the report  provided  by an
independent  public  accountant,  after conducting a review in compliance with
the  Uniform  Single  Attestation  Program  for  Mortgage  Bankers  or similar
standard  as set  forth  in the  Pooling  and  Servicing  Agreement,  that  is
included in these reports.

            In giving the  certifications  above, I have reasonably  relied on
the information provided to me by the following  unaffiliated  parties:  [each
Servicer, the Master Servicer, the Trustee or Trust Administrator].

--------------------------------------------------------------------------------

            Capitalized  terms used but not defined  herein have the  meanings
ascribed to them in the  Pooling and  Servicing  Agreement,  dated  January 1,
2005 (the  "Pooling  and  Servicing  Agreement"),  among  Credit  Suisse First
Boston  Mortgage  Securities  Corp.,  as  depositor  (the  "Depositor"),   DLJ
Mortgage  Capital,  Inc., as seller (in such capacity,  the "Seller"),  Select
Portfolio  Servicing,  Inc., as a servicer (in such  capacity,  a "Servicer"),
Wilshire  Credit  Corporation,  as special  servicer,  (in such capacity,  the
"Special  Servicer"),  HSBC Bank USA,  National  Association  as trustee  (the
"Trustee"),  Wells  Fargo  Bank,  N.A.,  as a servicer  (in such  capacity,  a
"Servicer")   as  trust   administrator   (in  such   capacity,   the   "Trust
Administrator")  and  as  master  servicer  (in  such  capacity,  the  "Master
Servicer"), and the other servicers that are signatories thereto.

                                                ______________________________
                                                [Name]
                                                [Title]
                                                [Date]

--------------------------------------------------------------------------------

                                  EXHIBIT U

                  FORM OF TRUST ADMINISTRATOR CERTIFICATION

      Re:   Credit Suisse First Boston Mortgage Securities Corp.,
            Adjustable Rate Mortgage Trust 2005-1,
            Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series
            2005-1

            Wells  Fargo  Bank,  N.A.  (the  "Trust   Administrator")   hereby
certifies  to Credit  Suisse  First  Boston  Mortgage  Securities  Corp.  (the
"Depositor"),  and each Person,  if any, who "controls"  the Depositor  within
the  meaning of the  Securities  Act of 1933,  as amended,  and its  officers,
directors  and  affiliates,  and with the  knowledge and intent that they will
rely upon this certification, that:

            1.    The Trust  Administrator  has reviewed the annual  report on
Form 10-K for the fiscal  year [___],  and all reports on Form 8-K  containing
distribution  reports filed in respect of periods included in the year covered
by that annual  report,  of the  Depositor  relating  to the  above-referenced
trust;

            2.    Based on the Trust Administrator's  knowledge,  and assuming
the  accuracy  and  completeness  of the  information  supplied  to the  Trust
Administrator  by the Master  Servicer  and each  Servicer,  the  distribution
information in the distribution  reports  contained in all reports on Form 8-K
included in the year covered by the annual  report on Form 10-K for the fiscal
year [___],  prepared by the Trust  Administrator,  taken as a whole, does not
contain any untrue  statement  of a material  fact or omit to state a material
fact  required by the Pooling and Servicing  Agreement to be included  therein
and  necessary  to make the  statements  made,  in light of the  circumstances
under which such  statements  were made,  not misleading as of the last day of
the period covered by that annual report; and

            3.    Based   on  the   Trust   Administrator's   knowledge,   the
distribution  information  required to be provided by the Trust  Administrator
under the Pooling and Servicing Agreement is included in these reports.

--------------------------------------------------------------------------------

            Capitalized  terms used but not defined  herein have the  meanings
ascribed  to  them  in  the  Pooling  and  Servicing  Agreement,  dated  as of
January 1,  2005 (the "Pooling and Servicing Agreement"),  among Credit Suisse
First Boston Mortgage  Securities Corp., as depositor (the  "Depositor"),  DLJ
Mortgage  Capital,  Inc., as seller (in such capacity,  the "Seller"),  Select
Portfolio  Servicing,  Inc., as a servicer (in such  capacity,  a "Servicer"),
Wilshire  Credit  Corporation,  as special  servicer  (in such  capacity,  the
"Special  Servicer"),  HSBC Bank USA,  National  Association,  as trustee (the
"Trustee"),  Wells Fargo Bank, N.A., as trust administrator (in such capacity,
the "Trust  Administrator"),  as a Servicer (in such  capacity,  a "Servicer")
and Master Servicer (in such capacity,  the "Master Servicer"),  and the other
servicers that are signatories thereto.

                                                Wells Fargo Bank, N.A.
                                                as Trust Administrator

                                                By:___________________________
                                                [Name]
                                                [Title]
                                                [Date]

--------------------------------------------------------------------------------

                                 EXHIBIT V-1

                    FORM OF MASTER SERVICER CERTIFICATION

      Re:   Credit Suisse First Boston Mortgage Securities Corp.,
            Adjustable Rate Mortgage Trust 2005-1,
            Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series
            2005-1

            Wells  Fargo  Bank,  N.A.  (the  "Master   Servicer"),   certifies
pursuant to  Section 10.13  (d)(i) of the Pooling and  Servicing  Agreement to
the  Depositor,   the  Trust  Administrator  and  each  Person,  if  any,  who
"controls" the Depositor or the Trust Administrator  within the meaning of the
Securities  Act of  1933,  as  amended,  and  their  respective  officers  and
directors with respect to the calendar year immediately  preceding the date of
this Certificate (the "Relevant Year"), as follows:

            1.    For  purposes of this  Certificate,  "Relevant  Information"
means the information in the certificate  provided pursuant to Section 3.16 of
the Pooling and Servicing Agreement (the "Annual Compliance  Certificate") for
the  Relevant  Year and the  information  in all  servicing  reports  required
pursuant to the Pooling and  Servicing  Agreement to be provided by the Master
Servicer to the Trust  Administrator  during the Relevant  Year.  Based on the
Master Servicer's knowledge, the Relevant Information,  taken as a whole, does
not  contain  any  untrue  statement  of a  material  fact or omit to  state a
material  fact  required to be stated  therein  which is necessary to make the
statements  made  therein,  in light of the  circumstances  under  which  such
statements were made, not misleading as of the last day of the Relevant Year.

            2.    The Relevant  Information has been provided to those Persons
entitled to receive it.

            3.    Based upon the review  required by the Pooling and Servicing
Agreement and except as disclosed in the Annual Compliance  Certificate or the
accountants'  statement  provided  pursuant to Section 3.17 of the Pooling and
Servicing  Agreement,  to the best of the  Master  Servicer's  knowledge,  the
Master Servicer has fulfilled its obligations  under the Pooling and Servicing
Agreement throughout the Relevant Year.

            Capitalized  terms used but not defined  herein have the  meanings
ascribed to them in the  Pooling and  Servicing  Agreement,  dated  January 1,
2005 (the  "Pooling  and  Servicing  Agreement"),  among  Credit  Suisse First
Boston  Mortgage  Securities  Corp.,  as  depositor  (the  "Depositor"),   DLJ
Mortgage  Capital,  Inc., as seller (in such capacity,  the "Seller"),  Select
Portfolio  Servicing,  Inc., as a servicer (in such  capacity,  a "Servicer"),
Wilshire  Credit  Corporation,  as special  servicer  (in such  capacity,  the
"Special  Servicer"),  HSBC Bank USA,  National  Association  as trustee  (the
"Trustee"),  Wells Fargo Bank, N.A. as trust  administrator (in such capacity,
the "Trust  Administrator"),  as a servicer (in such  capacity,  a "Servicer")
and Master Servicer (in such capacity,  the "Master Servicer"),  and the other
servicers that are signatories thereto.

                                                Wells Fargo Bank, N.A.
                                                as Master Servicer

                                                By:___________________________
                                                [Name]
                                                [Title]
                                                [Date]

--------------------------------------------------------------------------------

                                 EXHIBIT V-2

                        FORM OF SERVICER CERTIFICATION

      Re:   Credit Suisse First Boston Mortgage Securities Corp.,
            Adjustable Rate Mortgage Trust 2005-1,
            Adjustable Rate Mortgage-Backed Pass-Through Certificates, Series
            2005-1

            I, [name of  certifying  individual],  a duly  elected  and acting
officer of [__________________________]  (the "Servicer"), certify pursuant to
Section 10.13(d)(iii)   of  the  Pooling  and   Servicing   Agreement  to  the
Depositor,  the Trust  Administrator  and each Person,  if any, who "controls"
the Depositor or the Trust Administrator  within the meaning of the Securities
Act of 1933, as amended,  and their  respective  officers and directors,  with
respect  to  the  calendar  year  immediately   preceding  the  date  of  this
Certificate (the "Relevant Year"), as follows:

            1.    For  purposes of this  Certificate,  "Relevant  Information"
means the information in the certificate  provided pursuant to Section 3.16 of
the Pooling and Servicing Agreement (the "Annual Compliance  Certificate") for
the  Relevant  Year and the  information  in all  servicing  reports  required
pursuant  to  the  Pooling  and  Servicing  Agreement  to be  provided  by the
Servicer to the Trust  Administrator  during the  Relevant  Year.  Based on my
knowledge,  the Relevant  Information,  taken as a whole, does not contain any
untrue  statement of a material fact or omit to state a material fact required
to be stated therein which is necessary to make the  statements  made therein,
in light of the  circumstances  under  which such  statements  were made,  not
misleading as of the last day of the Relevant Year.

            2.    The Relevant  Information has been provided to those Persons
entitled to receive it.

            3.    I am responsible  for reviewing the activities  performed by
the Servicer  under the Pooling and  Servicing  Agreement  during the Relevant
Year.  Based upon the review  required by the Pooling and Servicing  Agreement
and  except  as  disclosed  in  the  Annual  Compliance   Certificate  or  the
accountants'  statement  provided  pursuant to Section 3.17 of the Pooling and
Servicing Agreement,  to the best of my knowledge,  the Servicer has fulfilled
its  obligations  under the Pooling and  Servicing  Agreement  throughout  the
Relevant Year.

            Capitalized  terms used but not defined  herein have the  meanings
ascribed to them in the  Pooling and  Servicing  Agreement,  dated  January 1,
2005 (the  "Pooling  and  Servicing  Agreement"),  among  Credit  Suisse First
Boston  Mortgage  Securities  Corp.,  as  depositor  (the  "Depositor"),   DLJ
Mortgage  Capital,  Inc., as seller (in such capacity,  the "Seller"),  Select
Portfolio  Servicing,  Inc., as a servicer (in such  capacity,  a "Servicer"),
Wilshire  Credit  Corporation,  as special  servicer  (in such  capacity,  the
"Special  Servicer"),  HSBC Bank USA,  National  Association  as trustee  (the
"Trustee"),  Wells Fargo Bank, N.A., as trust administrator (in such capacity,
the "Trust Administrator"),  as a servicer (in such capacity, a "Servicer) and
Master  Servicer,  (in such capacity,  the "Master  Servicer"),  and the other
servicers that are signatories thereto.

                                                [______________________]
                                                as Servicer

                                                By:___________________________
                                                Name:
                                                Title:
                                                Date:

--------------------------------------------------------------------------------

                                  SCHEDULE I

                            MORTGAGE LOAN SCHEDULE

                           (Provided Upon Request)

--------------------------------------------------------------------------------

                                 SCHEDULE IIA

    Representations and Warranties of Seller - DLJ Mortgage Capital, Inc.

            DLJMC,   in   its   capacity   as   Seller,   hereby   makes   the
representations  and  warranties  set  forth  in  this  Schedule  IIA  to  the
Depositor,  the Trustee and the Trust  Administrator,  as of the Closing Date,
or if so  specified  herein,  as of the Cut off Date or such other date as may
be  specified.  Capitalized  terms used but not defined  herein shall have the
meanings  assigned thereto in the Pooling and Servicing  Agreement dated as of
January 1,  2005 (the  "Agreement")  among Credit Suisse First Boston Mortgage
Securities Corp., as Depositor,  DLJ Mortgage Capital, Inc., as Seller, Select
Portfolio  Servicing,  Inc., as a Servicer,  Wilshire Credit  Corporation,  as
Special  Servicer,  HSBC Bank USA,  National  Association,  as Trustee,  Wells
Fargo Bank, N.A., as a Servicer,  Trust Administrator and Master Servicer, and
the other  servicers  that are  signatories  thereto.  DLJMC is a  corporation
duly  organized,  validly  existing and in good standing under the laws of the
state of its incorporation;

            (i)         DLJMC has full  corporate  power to own its  property,
      to carry on its  business as presently  conducted  and to enter into and
      perform its obligations under this Agreement;

            (ii)        the execution and delivery by DLJMC of this  Agreement
      have been duly authorized by all necessary  corporate action on the part
      of DLJMC; and neither the execution and delivery of this Agreement,  nor
      the consummation of the transactions  herein  contemplated  hereby,  nor
      compliance with the provisions  hereof,  will conflict with or result in
      a breach of, or  constitute a default  under,  any of the  provisions of
      any  law,  governmental  rule,  regulation,  judgment,  decree  or order
      binding on DLJMC or its properties or the  certificate of  incorporation
      or by-laws of DLJMC, except those conflicts,  breaches or defaults which
      would not  reasonably be expected to have a material  adverse  effect on
      DLJMC's  ability  to enter into this  Agreement  and to  consummate  the
      transactions contemplated hereby;

            (iii) the  execution,  delivery and  performance  by DLJMC of this
      Agreement and the consummation of the transactions  contemplated  hereby
      do not require the consent or approval  of, the giving of notice to, the
      registration  with, or the taking of any other action in respect of, any
      state, federal or other governmental  authority or agency,  except those
      consents,  approvals,  notices,  registrations  or other actions as have
      already  been  obtained,  given  or made  and,  in  connection  with the
      recordation  of the  Mortgages,  powers of  attorney or  assignments  of
      Mortgages not yet completed;

            (iv)  this  Agreement  has been duly  executed  and  delivered  by
      DLJMC and,  assuming due  authorization,  execution  and delivery by the
      Trustee,  the Trust Administrator,  the Master Servicer,  the Servicers,
      the Special Servicer and the Depositor,  constitutes a valid and binding
      obligation of DLJMC enforceable  against it in accordance with its terms
      (subject to applicable  bankruptcy and insolvency laws and other similar
      laws affecting the  enforcement  of the rights of creditors  generally);
      and

            (v)   to  the   knowledge   of  DLJMC,   there  are  no   actions,
      litigation,  suits or  proceedings  pending or threatened  against DLJMC
      before  or  by  any  court,   administrative   agency,   arbitrator   or
      governmental   body  (i)  with  respect  to  any  of  the   transactions
      contemplated  by this Agreement or (ii) with respect to any other matter
      which in the  judgment of DLJMC if  determined  adversely to DLJMC would
      reasonably  be expected  to  materially  and  adversely  affect  DLJMC's
      ability to perform its obligations  under this  Agreement;  and DLJMC is
      not in default  with  respect to any order of any court,  administrative
      agency,  arbitrator  or  governmental  body  so  as  to  materially  and
      adversely affect the transactions contemplated by this Agreement.

--------------------------------------------------------------------------------

                                 SCHEDULE IIB

  Representations and Warranties of Master Servicer - Wells Fargo Bank, N.A.

            Wells Fargo, in its capacity as Master Servicer,  hereby makes the
representations  and  warranties  set  forth  in  this  Schedule  IIB  to  the
Depositor,  the Trust  Administrator and the Trustee,  as of the Closing Date,
or if so  specified  herein,  as of the Cut-off Date or such other date as may
be specified.

            (i)   Wells Fargo is a national  banking  association duly formed,
      validly  existing and in good  standing and is qualified  under the laws
      of each state where  required by applicable  law or is otherwise  exempt
      under applicable law from such qualification.

            (ii)  Wells  Fargo  has  all   requisite   organizational   power,
      authority  and capacity to enter into the  Agreement  and to perform the
      obligations  required of it thereunder.  The Agreement (assuming the due
      authorization  and  execution  of the  Agreement  by the  other  parties
      thereto)  constitutes  a valid and legally  binding  agreement  of Wells
      Fargo  enforceable  in  accordance  with  its  terms,   except  as  such
      enforceability  may be limited by  bankruptcy,  insolvency,  moratorium,
      reorganization and similar laws, and by equitable  principles  affecting
      the enforceability of the rights of creditors.

            (iii) None of the  execution  and delivery of the  Agreement,  the
      consummation  of any  other  transaction  contemplated  therein,  or the
      fulfillment  of or  compliance  with the  terms of the  Agreement,  will
      result in the  breach of, or  constitute  a default  under,  any term or
      provision  of the  organizational  documents  of Wells Fargo or conflict
      with,  result in a material  breach,  violation  or  acceleration  of or
      constitute  a material  default  under,  the terms of any  indenture  or
      other  agreement  or  instrument  to which  Wells Fargo is a party or by
      which it is  bound,  or any  statute,  order,  judgment,  or  regulation
      applicable to Wells Fargo of any court, regulatory body,  administrative
      agency or governmental body having jurisdiction over Wells Fargo.

            (iv)  There  is  no  action,  suit,  proceeding  or  investigation
      pending, or to Wells Fargo's knowledge  threatened,  against Wells Fargo
      before any court,  administrative agency or other tribunal (a) asserting
      the   invalidity   of  the   Agreement,   (b)  seeking  to  prevent  the
      consummation  of any of the  transactions  contemplated  thereby  or (c)
      which might  materially  and adversely  affect the  performance by Wells
      Fargo of its obligations  under, or the validity or  enforceability  of,
      the Agreement.

            (v)   No consent,  approval,  authorization or order of any court,
      regulatory  body or  governmental  agency  or court is  required,  under
      state or federal law prior to the  execution,  delivery and  performance
      by Wells Fargo of the Agreement or the  consummation of the transactions
      contemplated by the Agreement.

--------------------------------------------------------------------------------

                                 SCHEDULE IIC

Representations and Warranties of Servicer - GreenPoint Mortgage Funding, Inc.

            GreenPoint,   in  its  capacity  as  Servicer,  hereby  makes  the
representations  and  warranties  set  forth  in  this  Schedule  IIC  to  the
Depositor,  the Trustee,  the Trust Administrator and the Master Servicer,  as
of the Closing  Date,  or if so  specified  herein,  as of the Cut-off Date or
such other date as may be specified.

            (i)   GreenPoint is a corporation  duly formed,  validly  existing
and in good standing under the laws of the  jurisdiction of its  incorporation
and is  qualified  under the laws of each state where  required by  applicable
law or is otherwise exempt under applicable law from such qualification.

            (ii)  GreenPoint has all requisite corporate power,  authority and
capacity to enter into the Agreement and to perform the  obligations  required
of  it  thereunder.   The  Agreement   (assuming  the  due  authorization  and
execution of the Agreement by the other parties  thereto)  constitutes a valid
and legally  binding  agreement of GreenPoint  enforceable in accordance  with
its  terms,  except  as such  enforceability  may be  limited  by  bankruptcy,
insolvency,  moratorium,  reorganization  and similar  laws,  and by equitable
principles affecting the enforceability of the rights of creditors.

            (iii) None of the  execution  and delivery of the  Agreement,  the
consummation  of  any  other   transaction   contemplated   therein,   or  the
fulfillment of or compliance  with the terms of the Agreement,  will result in
the breach of, or  constitute  a default  under,  any term or provision of the
organizational  documents of GreenPoint or conflict with, result in a material
breach,  violation or acceleration of or constitute a material  default under,
the  terms  of any  indenture  or  other  agreement  or  instrument  to  which
GreenPoint  is a  party  or by  which  it is  bound,  or any  statute,  order,
judgment,  or regulation  applicable  to  GreenPoint of any court,  regulatory
body,  administrative  agency or governmental  body having  jurisdiction  over
GreenPoint.

            (iv)  There  is  no  action,  suit,  proceeding  or  investigation
pending, or to GreenPoint's  knowledge  threatened,  against GreenPoint before
any  court,   administrative  agency  or  other  tribunal  (a)  asserting  the
invalidity of the Agreement,  (b) seeking to prevent the  consummation  of any
of the  transactions  contemplated  thereby or (c) which might  reasonably  be
expected to materially and adversely  affect the  performance by GreenPoint of
its obligations under, or the validity or enforceability of, the Agreement.

            (v)   No consent,  approval,  authorization or order of any court,
regulatory  body or governmental  agency or court is required,  under state or
federal law prior to the execution,  delivery and performance by GreenPoint of
the Agreement or the  consummation  of the  transactions  contemplated  by the
Agreement.

            (vi)  With  respect to each  GreenPoint  Serviced  Mortgage  Loan,
GreenPoint has fully  furnished,  in accordance with the Fair Credit Reporting
Act  and its  implementing  regulations,  accurate  and  complete  information
(e.g.,  favorable and  unfavorable)  on its borrower  credit files to Equifax,
Experian and Trans Union Credit Information Company, on a monthly basis.

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                                 SCHEDULE IID

Representations and Warranties of Servicer - Select Portfolio Servicing, Inc.

            SPS, in its  capacities as Servicer and Special  Servicer,  hereby
makes the  representations  and  warranties  set forth in this Schedule IID to
the Depositor,  the Trustee,  the Trust Administrator and the Master Servicer,
as of the Closing Date, or if so specified  herein,  as of the Cut-off Date or
such other date as may be specified.

            (vi)  SPS is a corporation  duly formed,  validly  existing and in
      good standing under the laws of the  jurisdiction  of its  incorporation
      and is  qualified  under  the  laws  of each  state  where  required  by
      applicable  law or is otherwise  exempt under  applicable  law from such
      qualification.

            (vii) SPS  has  all  requisite  corporate  power,   authority  and
      capacity  to enter into the  Agreement  and to perform  the  obligations
      required   of  it   thereunder.   The   Agreement   (assuming   the  due
      authorization  and  execution  of the  Agreement  by the  other  parties
      thereto)  constitutes  a valid  and  legally  binding  agreement  of SPS
      enforceable in accordance with its terms,  except as such enforceability
      may be limited by  bankruptcy,  insolvency,  moratorium,  reorganization
      and  similar   laws,   and  by  equitable   principles   affecting   the
      enforceability of the rights of creditors.

            (viii)      None of the execution  and delivery of the  Agreement,
      the consummation of any other transaction  contemplated  therein, or the
      fulfillment  of or  compliance  with the  terms of the  Agreement,  will
      result in the  breach of, or  constitute  a default  under,  any term or
      provision  of the  organizational  documents  of SPS or  conflict  with,
      result in a material breach,  violation or acceleration of or constitute
      a material  default under, the terms of any indenture or other agreement
      or  instrument  to which SPS is a party or by which it is bound,  or any
      statute,  order, judgment, or regulation applicable to SPS of any court,
      regulatory  body,  administrative  agency or  governmental  body  having
      jurisdiction over SPS.

            (ix)  There  is  no  action,  suit,  proceeding  or  investigation
      pending, or to SPS' knowledge threatened,  against SPS before any court,
      administrative  agency or other tribunal (a) asserting the invalidity of
      the  Agreement,  (b) seeking to prevent the  consummation  of any of the
      transactions  contemplated  thereby  or (c) which  might  reasonably  be
      expected to materially  and adversely  affect the  performance by SPS of
      its  obligations  under,  or the  validity  or  enforceability  of,  the
      Agreement.

            (x)   No consent,  approval,  authorization or order of any court,
      regulatory  body or  governmental  agency  or court is  required,  under
      state or federal law prior to the  execution,  delivery and  performance
      by  SPS of  the  Agreement  or  the  consummation  of  the  transactions
      contemplated by the Agreement.

            (xi)  With respect to each SPS Serviced  Mortgage  Loan and to the
      extent SPS has serviced any of the SPS Serviced  Mortgage Loans prior to
      the date of the Agreement,  SPS has fully furnished,  in accordance with
      the  Fair  Credit  Reporting  Act  and  its  implementing   regulations,
      accurate and complete  information (e.g.,  favorable and unfavorable) on
      its borrower  credit  files to Equifax,  Experian and Trans Union Credit
      Information Company, on a monthly basis.

--------------------------------------------------------------------------------

                                 SCHEDULE IIE

 Representations and Warranties of Servicer - U.S. Bank National Association

            U.S.  Bank,  in  its  capacity  as  Servicer,   hereby  makes  the
representations  and  warranties  set  forth  in  this  Schedule  IIE  to  the
Depositor,  the Trustee,  the Trust Administrator and the Master Servicer,  as
of the Closing  Date,  or if so  specified  herein,  as of the Cut-off Date or
such other date as may be specified.

            (vi)  U.S. Bank is a  corporation  duly formed,  validly  existing
      and  in  good  standing  under  the  laws  of  the  jurisdiction  of its
      incorporation  and is  qualified  under  the  laws of each  state  where
      required by applicable law or is otherwise  exempt under  applicable law
      from such qualification.

            (vii) U.S. Bank has all requisite  corporate power,  authority and
      capacity  to enter into the  Agreement  and to perform  the  obligations
      required   of  it   thereunder.   The   Agreement   (assuming   the  due
      authorization  and  execution  of the  Agreement  by the  other  parties
      thereto)  constitutes a valid and legally binding agreement of U.S. Bank
      enforceable in accordance with its terms,  except as such enforceability
      may be limited by  bankruptcy,  insolvency,  moratorium,  reorganization
      and  similar   laws,   and  by  equitable   principles   affecting   the
      enforceability of the rights of creditors.

            (viii)      None of the execution  and delivery of the  Agreement,
      the consummation of any other transaction  contemplated  therein, or the
      fulfillment  of or  compliance  with the  terms of the  Agreement,  will
      result in the  breach of, or  constitute  a default  under,  any term or
      provision  of the  organizational  documents  of U.S.  Bank or  conflict
      with,  result in a material  breach,  violation  or  acceleration  of or
      constitute  a material  default  under,  the terms of any  indenture  or
      other  agreement or instrument to which U.S. Bank is a party or by which
      it is bound, or any statute,  order,  judgment, or regulation applicable
      to U.S. Bank of any court,  regulatory  body,  administrative  agency or
      governmental body having jurisdiction over U.S. Bank.

            (ix)  There  is  no  action,  suit,  proceeding  or  investigation
      pending,  or to U.S.  Bank's  knowledge  threatened,  against U.S.  Bank
      before any court,  administrative agency or other tribunal (a) asserting
      the   invalidity   of  the   Agreement,   (b)  seeking  to  prevent  the
      consummation  of any of the  transactions  contemplated  thereby  or (c)
      which might  reasonably be expected to materially  and adversely  affect
      the performance by U.S. Bank of its  obligations  under, or the validity
      or enforceability of, the Agreement.

            (x)   No consent,  approval,  authorization or order of any court,
      regulatory  body or  governmental  agency  or court is  required,  under
      state or federal law prior to the  execution,  delivery and  performance
      by U.S. Bank of the Agreement or the  consummation  of the  transactions
      contemplated by the Agreement.

            (xi)  With respect to each U.S.  Bank  Serviced  Mortgage Loan and
      to the extent  U.S.  Bank has  serviced  any of the U.S.  Bank  Serviced
      Mortgage Loans prior to the date of the  Agreement,  U.S. Bank has fully
      furnished,  in  accordance  with the Fair Credit  Reporting  Act and its
      implementing  regulations,  accurate  and  complete  information  (e.g.,
      favorable  and  unfavorable)  on its  borrower  credit files to Equifax,
      Experian and Trans Union Credit Information Company, on a monthly basis.

--------------------------------------------------------------------------------

                                 SCHEDULE IIF

      Representations and Warranties of Servicer - Wells Fargo Bank, N.A.

            Wells Fargo Bank,  N.A. in its capacity as Servicer,  hereby makes
the  representations  and  warranties  set forth in this  Schedule  IIF to the
Depositor,  the Trustee and the Trust  Administrator,  as of the Closing Date,
or if so  specified  herein,  as of the Cut-off Date or such other date as may
be specified.

                  (i)   Wells  Fargo is a national  banking  association  duly
      organized and in good  standing  under the laws of the United States and
      is qualified  under the laws of each state where  required by applicable
      law or is otherwise exempt under applicable law from such qualification.

                  (ii)  Wells  Fargo  has  all  requisite   corporate   power,
      authority  and capacity to enter into the  Agreement  and to perform the
      obligations  required of it thereunder.  The Agreement (assuming the due
      authorization  and  execution  of the  Agreement  by the  other  parties
      thereto)  constitutes  a valid and legally  binding  agreement  of Wells
      Fargo  enforceable  in  accordance  with  its  terms,   except  as  such
      enforceability  may  be  limited  by  liquidation,  conservatorship  and
      similar  laws   administered   by  the  FDIC   affecting   the  contract
      obligations of insured banks, and by equitable  principles affecting the
      enforceability of the rights of creditors.

                  (iii) None of the execution  and delivery of the  Agreement,
      the consummation of any other transaction  contemplated  therein, or the
      fulfillment  of or  compliance  with the  terms of the  Agreement,  will
      result in the  breach of, or  constitute  a default  under,  any term or
      provision  of the  organizational  documents  of Wells Fargo or conflict
      with,  result in a material  breach,  violation  or  acceleration  of or
      constitute  a material  default  under,  the terms of any  indenture  or
      other  agreement  or  instrument  to which  Wells Fargo is a party or by
      which it is  bound,  or any  statute,  order,  judgment,  or  regulation
      applicable to Wells Fargo of any court, regulatory body,  administrative
      agency or governmental body having jurisdiction over Wells Fargo.

                  (iv)  There is no action, suit,  proceeding or investigation
      pending, or to Wells Fargo's knowledge  threatened,  against Wells Fargo
      before any court,  administrative agency or other tribunal (a) asserting
      the   invalidity   of  the   Agreement,   (b)  seeking  to  prevent  the
      consummation  of any of the  transactions  contemplated  thereby  or (c)
      which might  materially  and adversely  affect the  performance by Wells
      Fargo of its obligations  under, or the validity or  enforceability  of,
      the Agreement.

                  (v)   No consent,  approval,  authorization  or order of any
      court,  regulatory  body or  governmental  agency or court is  required,
      under  state  or  federal  law  prior  to the  execution,  delivery  and
      performance by Wells Fargo of the Agreement or the  consummation  of the
      transactions contemplated by the Agreement.

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                                 SCHEDULE IIG

     Representations and Warranties of Special Servicer - Wilshire Credit
                                 Corporation

            Wilshire,  in its capacity as Special  Servicer,  hereby makes the
representations  and  warranties  set  forth  in  this  Schedule  IIG  to  the
Depositor,  the Trustee,  the Trust Administrator and the Master Servicer,  as
of the Closing  Date,  or if so  specified  herein,  as of the Cut-off Date or
such other date as may be specified.

            (i)   Wilshire is a corporation duly formed,  validly existing and
in good standing under the laws of the jurisdiction of its  incorporation  and
is qualified  under the laws of each state where required by applicable law or
is otherwise exempt under applicable law from such qualification.

            (ii)  Wilshire has all requisite  corporate  power,  authority and
capacity to enter into the Agreement and to perform the  obligations  required
of  it  thereunder.   The  Agreement   (assuming  the  due  authorization  and
execution of the Agreement by the other parties  thereto)  constitutes a valid
and legally binding  agreement of Wilshire  enforceable in accordance with its
terms,   except  as  such   enforceability   may  be  limited  by  bankruptcy,
insolvency,  moratorium,  reorganization  and  similar  laws and by  equitable
principles affecting the enforceability of the rights of creditors.

            (iii) None of the  execution  and delivery of the  Agreement,  the
consummation  of  any  other   transaction   contemplated   therein,   or  the
fulfillment of or compliance  with the terms of the Agreement,  will result in
the breach of, or  constitute  a default  under,  any term or provision of the
organizational  documents of Wilshire or conflict  with,  result in a material
breach,  violation or acceleration of or constitute a material  default under,
the terms of any indenture or other  agreement or instrument to which Wilshire
is a party  or by which it is  bound,  or any  statute,  order,  judgment,  or
regulation   applicable   to   Wilshire   of  any  court,   regulatory   body,
administrative agency or governmental body having jurisdiction over Wilshire.

            (iv)  There  is  no  action,  suit,  proceeding  or  investigation
pending, or to Wilshire's  knowledge  threatened,  against Wilshire before any
court,  administrative  agency or other  tribunal (a) asserting the invalidity
of the  Agreement,  (b)  seeking to  prevent  the  consummation  of any of the
transactions  contemplated  thereby or (c) which might  reasonably be expected
to  materially  and  adversely  affect  the  performance  by  Wilshire  of its
obligations under, or the validity or enforceability of, the Agreement.

            (v)   No consent,  approval,  authorization or order of any court,
regulatory  body or governmental  agency or court is required,  under state or
federal law prior to the  execution,  delivery and  performance by Wilshire of
the Agreement or the  consummation  of the  transactions  contemplated  by the
Agreement.

            (vi)  With  respect  to  each  Special  Serviced   Mortgage  Loan,
Wilshire has fully  furnished,  in accordance  with the Fair Credit  Reporting
Act  and its  implementing  regulations,  accurate  and  complete  information
(e.g.,  favorable and  unfavorable)  on its borrower  credit files to Equifax,
Experian and Trans Union Credit Information Company, on a monthly basis.

--------------------------------------------------------------------------------

                                 SCHEDULE III

           Representations and Warranties of DLJMC - Mortgage Loans

            DLJMC,   in   its   capacity   as   Seller,   hereby   makes   the
representations  and  warranties  set  forth  in  this  Schedule  III  to  the
Depositor,  the Trustee and the Trust  Administrator,  as of the Closing Date,
or if so  specified  herein,  as of the Cut off Date or such other date as may
be  specified,  with respect to the Mortgage  Loans  identified  on Schedule I
hereto, except as specified herein.

            (i)   The  information  set forth in Schedule  I, with  respect to
      the  Mortgage  Loans,  is  complete,  true and  correct in all  material
      respects;

            (ii)  [Reserved];

            (iii) Except  for  7  Mortgage  Loans  representing  approximately
      0.27% of the aggregate  Cut-off Date Principal of the Mortgage Loans, no
      Mortgage  Loan  will be 30 or more  days  delinquent  as of the  Cut-off
      Date.  No  Mortgage  Loan will be 60 or more days  delinquent  as of the
      Cut-off  Date.  There are no  material  defaults  under the terms of any
      Mortgage Loan;

            (iv)  All taxes,  governmental  assessments,  insurance  premiums,
      water, sewer and municipal  charges,  leasehold payments or ground rents
      which  previously  became due and owing have been paid,  or escrow funds
      have been  established  in an amount  sufficient  to pay for every  such
      escrowed  item which  remains  unpaid and which has been assessed but is
      not yet due and payable;

            (v)   The terms of the  Mortgage  Note and the  Mortgage  have not
      been  impaired,  waived,  altered or modified in any respect,  except by
      written  instruments  which have been  recorded or sent for recording to
      the extent any such  recordation  is required by law,  or,  necessary to
      protect the interest of the  Depositor.  No other  instrument of waiver,
      alteration or modification has been executed,  and no Mortgagor has been
      released,  in  whole  or in  part,  from the  terms  thereof  except  in
      connection with an assumption  agreement and which assumption  agreement
      is part of the  Mortgage  File and the terms of which are  reflected  in
      Schedule  IA;  the   substance  of  any  such  waiver,   alteration   or
      modification  has been  approved by the issuer of any  related  Mortgage
      Guaranty  Insurance  Policy and title  insurance  policy,  to the extent
      required by the related policies;

            (vi)  The  Mortgage  Note and the  Mortgage are not subject to any
      right  of  rescission,  set-off,  counterclaim  or  defense,  including,
      without limitation,  the defense of usury, nor will the operation of any
      of the terms of the Mortgage  Note or the  Mortgage,  or the exercise of
      any  right   thereunder,   render   the   Mortgage   Note  or   Mortgage
      unenforceable,  in  whole  or in  part,  or  subject  to  any  right  of
      rescission,  set-off,  counterclaim or defense, including the defense of
      usury,  and no  such  right  of  rescission,  set-off,  counterclaim  or
      defense has been asserted with respect thereto;

            (vii) All  buildings  or other  customarily  insured  improvements
      upon the Mortgaged  Property are insured by an insurer  acceptable under
      the FNMA Guides,  against loss by fire, hazards of extended coverage and
      such other  hazards as are  provided for in the FNMA Guides or by FHLMC,
      as well as all  additional  requirements  set forth in  Section 4.10  of
      this Agreement.  All such standard hazard policies are in full force and
      effect and on the date of  origination  contained  a standard  mortgagee
      clause  naming DLJMC and its  successors in interest and assigns as loss
      payee and such  clause is still in effect and all  premiums  due thereon
      have been paid.  If required  by the Flood  Disaster  Protection  Act of
      1973,  as amended,  the  Mortgage  Loan is covered by a flood  insurance
      policy  meeting  the  requirements  of  the  current  guidelines  of the
      Federal  Insurance  Administration  which  policy  conforms  to FNMA and
      FHLMC requirements,  as well as all additional requirements set forth in
      Section 4.10  of this  Agreement.  Such  policy was issued by an insurer
      acceptable under FNMA or FHLMC  guidelines.  The Mortgage  obligates the
      Mortgagor  thereunder to maintain all such insurance at the  Mortgagor's
      cost and expense,  and on the Mortgagor's  failure to do so,  authorizes
      the  holder  of  the  Mortgage  to  maintain   such   insurance  at  the
      Mortgagor's  cost and expense and to seek  reimbursement  therefor  from
      the Mortgagor;

            (viii)      Each  Mortgage  Loan at the time it was made  complied
      in all material  respects with all applicable  local,  state and federal
      laws,  including,  without limitation,  usury, equal credit opportunity,
      disclosure,  recording and all applicable  predatory and abusive lending
      laws;

            (ix)  The  related  Mortgage is a valid,  subsisting,  enforceable
      and  perfected  first  lien on the  Mortgaged  Property,  including  for
      Mortgage  Loans that are not  Cooperative  Loans,  all  buildings on the
      Mortgaged  Property and all  installations  and mechanical,  electrical,
      plumbing,   heating  and  air  conditioning   systems  affixed  to  such
      buildings,  and all additions,  alterations and replacements made at any
      time  with  respect  to  the  foregoing  securing  the  Mortgage  Note's
      original  principal  balance.  The Mortgage and the Mortgage Note do not
      contain any  evidence  of any  security  interest  or other  interest or
      right  thereto.  Such  lien is free  and  clear of all  adverse  claims,
      liens  and  encumbrances   having  priority  over  the  first  lien,  as
      applicable,   of  the   Mortgage   subject  only  to  (1)  the  lien  of
      non-delinquent  current real property taxes and  assessments not yet due
      and payable, (2) covenants, conditions and restrictions,  rights of way,
      easements  and  other  matters  of the  public  record as of the date of
      recording  which  are  acceptable  to  mortgage   lending   institutions
      generally  and either (A) which are referred to or otherwise  considered
      in the appraisal  made for the  originator of the Mortgage  Loan, or (B)
      which do not  adversely  affect  the  appraised  value of the  Mortgaged
      Property as set forth in such appraisal,  and (3) other matters to which
      like properties are commonly  subject which do not materially  interfere
      with  the  benefits  of the  security  intended  to be  provided  by the
      Mortgage or the use,  enjoyment,  value or  marketability of the related
      Mortgaged  Property.   Any  security  agreement,   chattel  mortgage  or
      equivalent  document  related to and  delivered in  connection  with the
      Mortgage Loan establishes and creates a valid,  subsisting,  enforceable
      and perfected  first lien and first  priority  security  interest on the
      property  described  therein,  and the Seller has the full right to sell
      and assign the same to the Depositor;

            (x)   The Mortgage Note and the related  Mortgage are original and
      genuine  and each is the  legal,  valid and  binding  obligation  of the
      maker thereof,  enforceable in all respects in accordance with its terms
      subject to bankruptcy, insolvency, moratorium,  reorganization and other
      laws of general  application  affecting  the rights of creditors  and by
      general equitable principles;

            (xi)  DLJMC or its  affiliate  is the sole  owner  of  record  and
      holder  of the  Mortgage  Loan  and the  indebtedness  evidenced  by the
      Mortgage Note.  Immediately  prior to the transfer and assignment to the
      Depositor  on  the  Closing  Date,  the  Mortgage  Loan,  including  the
      Mortgage  Note and the  Mortgage,  were not subject to an  assignment or
      pledge,  and  DLJMC  had good and  marketable  title to and was the sole
      owner  thereof and had full right to transfer and sell the Mortgage Loan
      to the  Depositor  free and  clear  of any  encumbrance,  equity,  lien,
      pledge,  charge,  claim or security  interest and has the full right and
      authority  subject to no  interest  or  participation  of, or  agreement
      with,  any  other  party,  to sell  and  assign  the  Mortgage  Loan and
      following the sale of the Mortgage  Loan,  the  Depositor  will own such
      Mortgage Loan free and clear of any encumbrance,  equity,  participation
      interest, lien, pledge, charge, claim or security interest;

            (xii) There are no  mechanics'  or similar  liens or claims  which
      have  been  filed  for  work,  labor  or  material  (and no  rights  are
      outstanding  that under law could give rise to such liens) affecting the
      related  Mortgaged  Property which are or may be liens prior to or equal
      to the lien of the related Mortgage;

            (xiii)      All  improvements  subject to the Mortgage  which were
      considered in determining the appraised value of the Mortgaged  Property
      lie wholly within the boundaries and building  restriction  lines of the
      Mortgaged  Property  (and wholly  within the project  with  respect to a
      condominium unit) except for de minimis  encroachments  permitted by the
      FNMA  Guide and  which  have been  noted on the  appraisal  or the title
      policy  affirmatively  insures  against  loss or damage by reason of any
      violation,  variation or  encroachment  adverse  circumstances  which is
      either  disclosed or would have been  disclosed  by an accurate  survey,
      and no improvements on adjoining  properties encroach upon the Mortgaged
      Property  except those which are insured  against by the title insurance
      policy  referred to in clause (v) above or are acceptable  under FNMA or
      FHLMC  guidelines and all  improvements  on the property comply with all
      applicable zoning and subdivision laws and ordinances;

            (xiv) The  Mortgaged  Property  is not  subject  to  any  material
      damage by waste, fire, earthquake,  windstorm,  flood or other casualty.
      At origination  of the Mortgage Loan there was, and there  currently is,
      no  proceeding  pending  for the total or  partial  condemnation  of the
      Mortgaged Property;

            (xv)  Each  Mortgage  Loan  has  been  serviced  in  all  material
      respects in compliance with accepted servicing practices;

            (xvi) With respect to each Cooperative  Loan, the related Mortgage
      is a valid,  enforceable and subsisting  first security  interest on the
      related  Cooperative  Shares securing the related Mortgage Note, subject
      only to (a) liens of the  Cooperative  Property  for unpaid  assessments
      representing   the   Mortgagor's  pro  rata  share  of  the  Cooperative
      Property's  payments for its blanket  mortgage,  current and future real
      property  taxes,   insurance   premiums,   maintenance  fees  and  other
      assessments to which like  collateral is commonly  subject and (b) other
      matters  to which  like  collateral  is  commonly  subject  which do not
      materially  interfere  with the benefits of the security  intended to be
      provided  by the  Security  Agreement.  There  are no liens  against  or
      security   interest  in  the   Cooperative   Shares   relating  to  each
      Cooperative Loan (except for unpaid  maintenance,  assessments and other
      amounts owed to the related  Cooperative  Property which individually or
      in the  aggregate  will  not  have a  material  adverse  effect  on such
      Cooperative  Loan),  which have priority over DLJMC's security  interest
      in such Cooperative Shares;

            (xvii)      The Mortgage Loan complies with all terms,  conditions
      and  requirements of the originator's  underwriting  standards in effect
      at the time of origination of such Mortgage Loan;

            (xviii)     Each  Mortgage Loan  constitutes a qualified  mortgage
      under   Section 860G(a)(3)(A)  of  the  Code  and  Treasury  Regulations
      Section 1.860G-2(a)(1);

            (xix) With respect to each  Mortgage  Loan sold by the Seller,  to
      the   knowledge   of  DLJMC,   (i)  no   borrower   obtained  a  prepaid
      single-premium  credit life, credit disability,  credit  unemployment or
      credit property  insurance  policy in connection with the origination of
      such  Mortgage  Loan,  (ii) the related  Servicer of each such  Mortgage
      Loan has fully  furnished,  in accordance with the Fair Credit Reporting
      Act and its implementing regulations,  accurate and complete information
      on its  borrower  credit  files to  Equifax,  Experian  and Trans  Union
      Credit  Information  Company,  on a monthly basis; and (iii) no Mortgage
      Loan  will  impose a  Prepayment  Premium  for a term in  excess of five
      years;

            (xx)  DLJMC  has  delivered  or  caused  to be  delivered  to  the
      Trustee or the Custodian on behalf of the Trustee the original  Mortgage
      bearing  evidence  that  such  instruments  have  been  recorded  in the
      appropriate  jurisdiction  where the  Mortgaged  Property  is located as
      determined  by DLJMC (or in lieu of the  original of the Mortgage or the
      assignment  thereof,  a duplicate or  conformed  copy of the Mortgage or
      the  instrument of  assignment,  if any,  together with a certificate of
      receipt  from DLJMC or the  settlement  agent who handled the closing of
      the Mortgage Loan,  certifying  that such copy or copies  represent true
      and  correct  copies  represent  true  and  correct   copy(ies)  of  the
      originals)  and  that  such  original(s)  have  been  or  are  currently
      submitted  to be  recorded  in the  appropriate  governmental  recording
      office of the jurisdiction  where the Mortgaged Property is located or a
      certification or receipt of the recording authority evidencing the same;

            (xxi) The Mortgage File  contains each of the documents  specified
      in Section 2.01(b) of this Agreement;

            (xxii)      No  Mortgage  Loan  sold by the  Seller  secured  by a
      Mortgaged  Property located in the State of Georgia was originated on or
      after  October 1, 2002 and  before  March 7, 2003 and no  Mortgage  Loan
      secured by Mortgaged  Property  located in the State of Georgia that was
      originated  on or after  March 7,  2003 is a "high  cost  home  loan" as
      defined in the Georgia Fair Lending Act (HB 1361), as amended;

            (xxiii)     With   respect   to   each   Cooperative   Loan,   the
      Cooperative  Shares that is pledged as security for the Cooperative Loan
      is held by a person as a  tenant-stockholder  (as defined in Section 216
      of the  Code)  in a  cooperative  housing  corporation  (as  defined  in
      Section 216 of the Code);

            (xxiv)      None of the  Mortgage  Loans  sold by the  Seller  are
      classified as (a) a "high cost  mortgage"  loan under the Home Ownership
      and Equity  Protection Act of 1994 or (b) a "high cost home," "covered,"
      "high  cost,"  "high  risk  home" or  "predatory"  loan  under any other
      applicable state, federal or local law;

            (xxv) With respect to each  Mortgage  Loan,  (a) the Mortgage Loan
      was  originated by a mortgagee  approved by the Secretary of Housing and
      Urban  Development  pursuant  to  sections  203 and 211 of the  National
      Housing  Act,  a  savings  and  loan  association,  a  savings  bank,  a
      commercial bank, credit union,  insurance company or similar institution
      which is supervised and examined by a federal or state  authority or (b)
      at the time the  Mortgage  Loan was  originated,  the  originator  was a
      mortgagee  duly  licensed  as  required  by the State  within  which the
      Mortgage  Loan  was  originated,  and was  subject  to  supervision  and
      examination conducted by the applicable State authority of such State;

            (xxvi)      With  respect  to  each   Mortgage  Loan  that  has  a
      Prepayment Premium feature,  each such Prepayment Premium is enforceable
      and, at the time such  Mortgage  Loan was  originated,  each  Prepayment
      Premium complied with applicable  federal,  state and local law, subject
      to federal preemption where applicable;

            (xxvii)     The  related  Servicer of each  Mortgage  Loan sold by
      the Seller  will  fully  furnish,  in  accordance  with the Fair  Credit
      Reporting Act and its  implementing  regulations,  accurate and complete
      information on its borrower credit files to Equifax,  Experian and Trans
      Union Credit Information Company, on a monthly basis;

            (xxviii)    [Reserved];

            (xxix)      With  respect  to the  Group 3,  Group 4 and  Group 5A
      Mortgage  Loans,  the original  principal  balance of each such Mortgage
      Loan is within  Freddie Mac's dollar amount limits for  conforming  one-
      to four-family Mortgage Loans;

            (xxx) Each  Mortgage  Loan that is  secured  by  residential  real
      property (or a leasehold interest therein) has a loan-to-value  ratio of
      100% or less by Cut-Off Date Principal Balance;

            (xxxi)      No  Mortgage  Loan sold by the  Seller is a "High Cost
      Loan" or  "Covered  Loan," as  applicable,  as such terms are defined in
      the Standard & Poor's LEVELS® Glossary,  Appendix E, in effect as of the
      Closing Date; and

            (xxxii)     With respect to any  Mortgage  Loan  originated  on or
      after August 1,  2004,  either (a) the related  Mortgage and the related
      Mortgage Note does not contain a mandatory  arbitration clause (that is,
      a clause that  requires the related  Mortgagor to submit to  arbitration
      to resolve  any  dispute  arising  out of or  relating in any way to the
      Mortgage  Loan) or (b) the related  Mortgage  and the  related  Mortgage
      Note  contained  a  mandatory  arbitration  clause  as  of  the  related
      origination  date  and  such  clause  has  or  will  be  waived  by  the
      originator  or an entity  designated  by the  Seller in writing no later
      than  sixty  (60) days  after the  related  Closing  Date  which  notice
      included  or  will  include  the  following  language:  "WE  ARE  HEREBY
      NOTIFYING  YOU THAT  THE  MANDATORY  ARBITRATION  CLAUSE  OF YOUR  LOAN,
      REQUIRING THAT YOU SUBMIT TO ARBITRATION TO RESOLVE ANY DISPUTE  ARISING
      OUT OF OR  RELATING IN ANY WAY TO YOUR  MORTGAGE  LOAN,  IS  IMMEDIATELY
      NULL AND VOID.  YOU ARE FREE TO CHOOSE TO  EXERCISE  ANY OF YOUR  RIGHTS
      OR ENFORCE  ANY  REMEDIES  UNDER YOUR  MORTGAGE  LOAN  THROUGH THE COURT
      SYSTEM." A copy of the written  notice  referred  to in the  immediately
      preceding  sentence,  if  applicable,  shall be  retained in the related
      Mortgage File.

--------------------------------------------------------------------------------

                                 SCHEDULE IV

                      Eligible Servicing Transfer Loans

--------------------------------------------------------------------------------

                                  APPENDIX A

              Calculation of Class Y Principal Reduction Amounts

Class Y Principal Reduction Amounts:

      (1)   For any  Distribution  Date the  amounts  by which  the  principal
balances of the  Class Y-1,  Class Y-2,  Class Y-3,  Class Y-4,  Class Y-5 and
Class Y-6 Certificates  respectively will be reduced on such distribution date
by the  allocation  of  Realized  Losses and the  distribution  of  principal,
determined as follows:

First  for each of Group 1,  Group 2,  Group 3,  Group 4,  Group 6 and Group 6
determine  the  weighted  average   pass-through   rate  for  that  Group  for
distributions   of  interest  that  will  be  made  on  the  next   succeeding
Distribution  Date  (the  "Group  Interest  Rate").  The  Principal  Reduction
Amount for each of the Class Y  Certificates  will be  determined  pursuant to
the "Generic solution for the Class Y Principal  Reduction  Amounts" set forth
below (the  "Generic  Solution")  by making  identifications  among the actual
Groups  and their  related  Class Y  and  Class Z  Certificates  and  weighted
average  pass-through  rates and the Groups named in the Generic  Solution and
their related Class Y and Class Z Certificates as follows:

A.  Determine  which  Group has the lowest  Group  Interest  Rate.  That Group
will be  identified  with  Group AA  and the Class Y and Class Z  Certificates
related to that Group will be  respectively  identified with the Class YAA and
Class ZAA  Certificates.  The  Group  Interest  Rate  for that  Group  will be
identified  with J%. If two or more  Groups  have the  lowest  Group  Interest
Rate pick one for this  purpose,  subject to the  restriction  that each Group
may be picked  only  once in the  course of any such  selections  pursuant  to
paragraphs A through F of this definition.

B.  Determine  which Group has the second  lowest Group  Interest  Rate.  That
Group  will  be   identified   with  Group BB  and  the  Class Y  and  Class Z
Certificates  related to that Group will be  respectively  identified with the
Class BB and Class ZBB  Certificates.  The Group  Interest Rate for that Group
will be  identified  with K%. If two or more  Groups  have the  second  lowest
Group  Interest  Rate pick one for this  purpose,  subject to the  restriction
that each Group may be picked  only once in the course of any such  selections
pursuant to paragraphs A through F of this definition.

C.  Determine  which Group has the third  lowest  Group  Interest  Rate.  That
Group  will  be   identified   with  Group CC  and  the  Class Y  and  Class Z
Certificates  related to that Group will be  respectively  identified with the
Class YCC and Class ZCC  Certificates.  The Group Interest Rate for that Group
will be  identified  with L%.  If two or more  Groups  have the  third  lowest
Group  Interest  Rate pick one for this  purpose,  subject to the  restriction
that each Group may be picked  only once in the course of any such  selections
pursuant to paragraphs A through F of this definition.

D.  Determine  which Group has the fourth  lowest Group  Interest  Rate.  That
Group  will  be   identified   with  Group DD  and  the  Class Y  and  Class Z
Certificates  related to that Group will be  respectively  identified with the
Class YDD and Class ZDD  Certificates.  The Group Interest Rate for that Group
will be  identified  with M%. If two or more  Groups  have the  fourth  lowest
Group  Interest  Rate pick one for this  purpose,  subject to the  restriction
that each Group may be picked  only once in the course of any such  selections
pursuant to paragraphs A through F of this definition.

E.  Determine  which Group has the fifth  lowest  Group  Interest  Rate.  That
Group  will  be   identified   with  Group EE  and  the  Class Y  and  Class Z
Certificates  related to that Group will be  respectively  identified with the
Class YEE and Class ZEE  Certificates.  The Group Interest Rate for that Group
will be  identified  with N%.  If two or more  Groups  have the  fifth  lowest
Group  Interest  Rate pick one for this  purpose,  subject to the  restriction
that each Group may be picked  only once in the course of any such  selections
pursuant to paragraphs A through F of this definition.

F.  Determine  which Group has the highest  Group  Interest  Rate.  That Group
will be  identified  with  Group FF  and the Class Y and Class Z  Certificates
related to that Group will be  respectively  identified with the Class YFF and
Class ZFF  Certificates.  The  Group  Interest  Rate  for that  Group  will be
identified  with O%. If two or more  Groups  have the  highest  Interest  Rate
pick one for this purpose,  subject to the restriction  that each Group may be
picked only once in the course of any such  selections  pursuant to paragraphs
A through F of this definition.

Second,  apply the Generic  Solution set forth below to determine  the Class Y
Principal   Reduction   Amounts   for  the   Distribution   Date   using   the
identifications made above.

Generic Solution for the Class Y Principal Reduction Amounts:

For any Distribution  Date, the amounts by which the principal balances of the
Class YAA,  Class YBB,  Class YCC,  Class YDD, Class YEE, Class YFF, Class YGG
and Class YHH  Certificates  respectively will be reduced on such Distribution
Date by the allocation of Realized  Losses and the  distribution of principal,
determined as follows:

For purposes of the succeeding  formulas the following  symbols shall have the
meanings set forth below:

J% =  the weighted  average  pass-through  rate on the Group AA mortgage loans
for interest to be distributed on the next succeeding Distribution Date.

K% =  the weighted  average  pass-through  rate on the Group BB mortgage loans
for interest to be distributed on   the next succeeding Distribution Date.

L% =  the weighted  average  pass-through  rate on the Group CC mortgage loans
for interest to be distributed on   the next succeeding Distribution Date.

M% =  the weighted  average  pass-through  rate on the Group DD mortgage loans
for interest to be distributed on the next succeeding Distribution Date.

N% =  the weighted  average  pass-through  rate on the Group EE mortgage loans
for interest to be distributed on   the next succeeding Distribution Date.

O% =  the weighted  average  pass-through  rate on the Group FF mortgage loans
for interest to be distributed on   the next succeeding Distribution Date.

For purposes of the succeeding  definitions and formulas,  it is required that
J%<=K%<=L%<=M%<=N%<=O%.

PJB =       the Group AA  Subordinate  Amount after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

PKB =       the Group BB  Subordinate  Amount after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

PLB = the Group CC Subordinate  Amount after the allocation of Realized Losses
      and distributions of principal on such Distribution Date.

PMB =       the Group DD  Subordinate  Amount after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

PNB =       the Group EE  Subordinate  Amount after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

POB =       the Group FF  Subordinate  Amount after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

R =   the Class CB Pass Through Rate
    =       (J%PJB + K%PKB + L%PLB + M%PMB + N%PNB + O%POB)/
                (PJB + PKB + PLB + PMB + PNB + POB)

R11 = the  weighted  average of the Group AA, Group BB, Group CC, Group DD and
      Group EE  Pass-Through  Rates after giving  effect to the  allocation of
      Realized  Losses  and  distributions  of  principal  to be  made on such
      Distribution Date
     =      {J% (Pj -Δ Pj) + K% (Pk -Δ Pk) + L% (Pl -Δ Pl) + M% (Pm -Δ Pm) + N% (Pn -Δ Pn) }/
                (Pj -Δ Pj + Pk -Δ Pk + Pl -Δ Pl + Pm -Δ Pm + Pn -Δ Pn)

R12 = the Group FF Pass-Through Rate
      =     O%

R21 = the  weighted  average of the Group AA,  Group BB, Group CC and Group DD
      Pass-Through  Rates after giving  effect to the  allocation  of Realized
      Losses and  distributions  of principal to be made on such  Distribution
      Date
     =      {J% (Pj -Δ Pj) + K% (Pk -Δ Pk) + L% (Pl -Δ Pl) + M% (Pm -Δ Pm) }/
                (Pj -Δ Pj + Pk -Δ Pk + Pl -Δ Pl + Pm -Δ Pm)

R22 = the weighted average of the Group EE and Group FF Pass-Through Rates
      =     {N% (Pn -Δ Pn) + O%(Po -Δ Po)}/(Pn -Δ Pn + Po -Δ Po)

R31 = the   weighted   average  of  the  Group  AA,  Group  BB  and  Group  CC
      Pass-Through  Rates after giving  effect to the  allocation  of Realized
      Losses and  distributions  of principal to be made on such  Distribution
      Date
     =      {(J% (Pj -Δ Pj) + K% (Pk -Δ Pk) + L% (Pl -Δ Pl) }/
                (Pj -Δ Pj + Pk -Δ Pk + Pl -Δ Pl)

R32 = the   weighted   average  of  the  Group  DD,   Group EE  and  Group  FF
      Pass-Through  Rates after giving  effect to the  allocation  of Realized
      Losses and  distributions  of principal to be made on such  Distribution
      Date
     =      { M% (Pm -Δ Pm) + N% (Pn -Δ Pn) + O% (Po -Δ Po)}/
                ( Pm -Δ Pm + Pn -Δ Pn + Po -Δ Po )

R41 = the  weighted  average of the Group AA and Group BB  Pass-Through  Rates
      after  giving  effect  to  the   allocation   of  Realized   Losses  and
      distributions of principal to be made on such Distribution Date
     =      {J% (Pj -Δ Pj) + K% (Pk -Δ Pk) }/
                (Pj -Δ Pj + Pk -Δ Pk )

R42 = the weighted  average of the Group CC,  Group DD,  Group EE and Group FF
      Pass-Through  Rates after giving  effect to the  allocation  of Realized
      Losses and  distributions  of principal to be made on such  Distribution
      Date
     =      { N% (Pn -Δ Pn) + O% (Po -Δ Po) + L% (Pl -Δ Pl) + M% (Pm -Δ Pm)}/
                ( Pn -Δ Pn + Po -Δ Po + Pl -Δ Pl + Pm -Δ Pm )

R51 = the Group AA Pass-Through  Rate after giving effect to the allocation of
      Realized  Losses  and  distributions  of  principal  to be  made on such
      Distribution Date
     =      J%

R52 = the weighted  average of the Group BB, Group CC, Group DD,  Group EE and
      Group FF  Pass-Through  Rates after giving  effect to the  allocation of
      Realized  Losses  and  distributions  of  principal  to be  made on such
      Distribution Date
     =      { M% (Pm -Δ Pm) + N% (Pn -Δ Pn) + O% (Po -Δ Po) + K% (Pk -Δ Pk) + L% (Pl -Δ Pl)}/
                ( Pm -Δ Pm + Pn -Δ Pn + Po -Δ Po + Pk -Δ Pk + Pl -Δ Pl )

r11 = the weighted average of the Class YAA,  Class YBB,  Class YCC, Class YDD
      and Class YEE Pass-Through Rates
     =      (J% Yj + K% Yk + L% Yl + M% Ym + N% Yn )/
                (Yj + Yk + Yl + Ym + Yn)

r12 = the Class YFF Pass-Through Rate
     =      O%

r21 = the  weighted  average  of  the  Class YAA,   Class YBB,  Class YCC  and
      Class YDD Pass-Through Rates
     =      (J% Yj + K% Yk + L% Yl + M% Ym )/(Yj + Yk + Yl + Ym )

r22 = the weighted average of the Class YEE and Class YFF Pass-Through Rates
     =      ( N% Yn + O% Yo )/( Yn + Yo )

r31 = the  weighted   average  of  the  Class YAA,   Class YBB  and  Class YCC
      Pass-Through Rates
     =      (J% Yj + K% Yk + L% Yl )/(Yj + Yk + Yl )

r32 = the  weighted   average  of  the  Class YDD,   Class YEE  and  Class YFF
      Pass-Through Rates
     =      ( O% Yo + M% Ym + N% Yn )/( Yo + Ym + Yn )

r41 = the weighted average of the Class YAA and Class YBB Pass-Through Rates
     =      (J% Yj + K% Yk )/(Yj + Yk )

r42 = the  weighted  average  of  the  Class YCC,   Class YDD,  Class YEE  and
      Class YFF Pass-Through Rates
     =      ( N% Yn + O% Yo + L% Yl + M% Ym )/( Yn + Yo + Yl + Ym )

r51 = the Class YAA
     =      J%

r52 = the weighted average of the Class YBB,  Class YCC,  Class YDD, Class YEE
      and Class YFF Pass-Through Rates
     =      ( M% Ym + N% Yn + O% Yo + K% Yk + L% Yl )/( Ym + Yn + Yo + Yk + Yl )

Yj =  the principal balance of the Class YAA  Certificates after distributions
      on the prior Distribution Date.

Yk =  the principal balance of the Class YBB  Certificates after distributions
      on the prior Distribution Date.

Yl =  the principal balance of the Class YCC  Certificates after distributions
      on the prior Distribution Date.

Ym =  the principal balance of the Class YDD  Certificates after distributions
      on the prior Distribution Date.

Yn =  the principal balance of the Class YEE  Certificates after distributions
      on the prior Distribution Date.

Yo =  the principal balance of the Class YFF  Certificates after distributions
      on the prior Distribution Date.

ΔYj =       the Class YAA Principal Reduction Amount.

ΔYk =       the Class YBB Principal Reduction Amount.

ΔYl =       the Class YCC Principal Reduction Amount.

ΔYm =       the Class YDD Principal Reduction Amount.

ΔYn =       the Class YEE Principal Reduction Amount.

ΔYo =       the Class YFF Principal Reduction Amount.

Zj =  the principal balance of the Class ZAA  Certificates after distributions
      on the prior Distribution Date.

Zk =  the principal balance of the Class ZBB  Certificates after distributions
      on the prior Distribution Date.

Zl =  the principal balance of the Class ZCC  Certificates after distributions
      on the prior Distribution Date.

Zm =  the principal balance of the Class ZDD  Certificates after distributions
      on the prior Distribution Date.

Zn =  the principal balance of the Class ZEE  Certificates after distributions
      on the prior Distribution Date.

Zo =  the principal balance of the Class ZFF  Certificates after distributions
      on the prior Distribution Date.

ΔZj =       the Class ZAA Principal Reduction Amount.

ΔZk =       the Class ZBB Principal Reduction Amount.

ΔZl =       the Class ZCC Principal Reduction Amount.

ΔZm =       the Class ZDD Principal Reduction Amount.

ΔZn =       the Class ZEE Principal Reduction Amount.

ΔZo =       the Class ZFF Principal Reduction Amount.

Pj =  the  aggregate   principal   balance  of  the  Class YAA  and  Class ZAA
      Certificates after distributions on the prior Distribution Date.
    = Yj + Zj

Pk =  the  aggregate   principal   balance  of  the  Class YBB  and  Class ZBB
      Certificates after distributions on the prior Distribution Date.
    = Yk + Zk

Pl =  the  aggregate   principal   balance  of  the  Class YCC  and  Class ZCC
      Certificates after distributions on the prior Distribution Date.
    = Yl + Zl =

Pm =  the  aggregate   principal   balance  of  the  Class YAA  and  Class ZAA
      Certificates after distributions on the prior Distribution Date.
    = Ym + Zm

Pn =  the  aggregate   principal   balance  of  the  Class YAA  and  Class ZAA
      Certificates after distributions on the prior Distribution Date.
    = Yn + Zn

Po =  the  aggregate   principal   balance  of  the  Class YAA  and  Class ZAA
      Certificates after distributions on the prior Distribution Date.
    = Yo + Zo

ΔPj = the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group AA mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group AA
      =     the aggregate of the Class YAA and Class ZAA  Principal  Reduction
      Amounts.
      =  Δ   Yj +Δ Zj

ΔPk = the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group BB mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group BB
      =     the aggregate of the Class YBB and Class ZBB  Principal  Reduction
                Amounts.
      =    Δ Yk + ΔZk

ΔPl=  the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group CC mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group CC
     =      the aggregate of the Class YCC and Class ZCC  Principal  Reduction
                Amounts.
     =    Δ Yl + ΔZl

ΔPm = the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group DD mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group DD
      =     the aggregate of the Class YDD and Class ZDD  Principal  Reduction
                Amounts.
      =    Δ Ym +Δ Zm

ΔPn = the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group EE mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group EE
      =     the aggregate of the Class YEE and Class ZEE  Principal  Reduction
                Amounts.
      =     ΔYn + ΔZn

ΔPo = the  aggregate  amount  of  principal   reduction  occurring  with
      respect to the Group FF mortgage loans from Realized  Losses or payments
      of principal to be allocated on such  Distribution  Date net of any such
      amounts  allocated  to the  Class  R-I  Certificate  or to any  class of
      principal  only  certificates  created by ratio  stripping  the mortgage
      loans of Group FF
      =     the aggregate of the Class YFF and Class ZFF  Principal  Reduction
                Amounts.
      =     ΔYo + ΔZo

 α=   .0005

γ1 =  (R - R11)/(R12 - R). If R>N%, γ 1 is a non-negative  number
      unless its denominator is zero, in which event it is undefined.

γ2 =  (R - R21)/(R22 - R). If R>M%, γ 2 is a non-negative  number
      unless its denominator is zero, in which event it is undefined.

γ3 =  (R - R31)/(R32 - R). If R>L%, γ 3 is a non-negative  number
      unless its denominator is zero, in which event it is undefined.

γ4 =  (R - R41)/(R42 - R). If R>K%, γ 4 is a non-negative  number
      unless its denominator is zero, in which event it is undefined.

γ5 =  (R - R51)/(R52 - R).  If R<K%, γ5 is a non-negative number.

If γ1 is  undefined, Δ Yj  = Yj,  ΔYk = Yk,  ΔYl = Yl,
      ΔYm = Ym, ΔYn = Yn, and ΔYo = (Yo/Po)ΔPo

If γ5 is zero, Δ Yj = (Yj/Pj)ΔPj, Δ Yk = Yk,Δ Yl
      = Yl, ΔYm = Ym, ΔYn = Yn, and ΔYo = Yo

In the  remaining  situations, Δ Yj, Δ Yk, Δ Yl,  ΔYm,
      ΔYn, and ΔYo shall be defined as follows:

I.  If R>N%, make the following additional definitions:

δ1Yj = 0,                                                          if R11< r11;

      Yj                                                          if R11> r11 and
                                                                      R11>N%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yj/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl +
            (R11 - M%)Ym },                                       if R11> r11 and
      N%>R11>M%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yj/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl },        if R11>r11 and
       M%>R11>L%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yj/
            {(R11 - J%)Yj + (R11 - K%)Yk },                       if R11>r11 and
      L%>R11>K%; and

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )/(R11 - J%),            if R11>r11 and K%>R11>J%.

δ1Yk =      0,                                               if R11< r11 and R11>K%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yk/
            { (R11 - K%)Yk + (R11 - L%)Yl + (R11 - M%)Ym +
            (R11 - N%)Yn },         if R11< r11 and R11<K%;

      Yk                                                          if R11>r11 and R11>N%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yk/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl +
            (R11 - M%)Ym },                                       if R11> r11 and
      N%>R11>M%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn  )Yk/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl },        if R11>r11 and
       M%>R11>L%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yk/
            {(R11 - J%)Yj + (R11 - K%)Yk },                       if R11> r11 and
      L%>R11>K%; and

      0,                                                          if R11> r11 and R11<K%.

δ1Yl = 0,                                                          if R11< r11 and R11>L%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn)Yl/
            { (R11 - L%)Yl + (R11 - M%)Ym + (R11 - N%)Yn },       if R11< r11 and
      K%<R11<L%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yl/
            { (R11 - K%)Yk + (R11 - L%)Yl + (R11 - M%)Ym +
            (R11 - N%)Yn },                                       if R11<r11 and R11<K%;

            Yl                                                    if R11> r11 and R11>N%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yl/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl +
            (R11 - M%)Ym },                                       if R11> r11 and
      N%>R11>M%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yl/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl },        if R11> r11 and
      M%>R11>L%;

      0,                                                          if R11> r11 and R11<L%.

δ1Ym = 0,                                                          if R11<r11 and R11>M%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Ym/
            { (R11 - M%)Ym + (R11 - N%)Yn },                      if R11< r11 and
      L%<R11<M%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Ym/
            { (R11 - L%)Yl + (R11 - M%)Ym + (R11 - N%)Yn },       if R11<r11 and
       K%<R11<L%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Ym/
            { (R11 - K%)Yk + (R11 - L%)Yl + (R11 - M%)Ym +
            (R11 - N%)Yn },                                       if R11<r11 and R11<K%;

                  Ym                                              if R11> r11 and R11>N%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Ym/
            {(R11 - J%)Yj + (R11 - K%)Yk + (R11 - L%)Yl +
            (R11 - M%)Ym },                                       if R11> r11 and
      N%>R11>M%;

      0,                                                          if R11> r11 and R11<M%.

δ1Yn =      0,                                                     if R11<r11 and R11>N%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )/
            { (R11 - N%)},                                        if R11<r11 and M%<R11<N%;

            (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yn/
            { (R11 - M%)Ym + (R11 - N%)Yn },                      if R11< r11 and
       L%<R11<M%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yn/
            { (R11 - L%)Yl + (R11 - M%)Ym + (R11 - N%)Yn },       if R11< r11 and
       K%<R11<L%;

      (R11- r11)( Yj + Yk + Yl + Ym + Yn )Yn/
            { (R11 - K%)Yk + (R11 - L%)Yl + (R11 - M%)Ym +
            (R11 - N%)Yn },                                       if R11<r11 and R11<K%;

            Yn                                                    if R11> r11 and R11>N%;

            0,                                                    if R11> r11 and R11<N%.

1δYj, δ1Yk, δ1Yl,δ 1Ym, and δ1Yn are numbers respectively between Yj, Yk, Yl, Ym and Yn and 0 such that
          {J%(Yj - δ1Yj ) + K%( Yk.-δ 1Yk) + L%( Yl.-δ 1Yl) + M%( Ym.-δ 1Ym) +
          N%( Yn.-δ 1Yn) }/
          (Yj - δ1Yj + Yk.-δ 1Yk + Yl.- δ1Yl + Ym.- δ1Ym + Yn.- δ1Yn )
          = R11.

Y11 =       Yj -δ 1Yj + Yk.- δ1Yk + Yl.- δ1Yl + Ym.- δ1Ym + Yn.-δ 1Yn

P11 =       Pj + Pk + Pl + Pm + Pn

Z11 =       Zj + Zk + Zl + Zm + Zn

ΔY11 =  Δ    Yj -δ 1Yj +Δ Yk.-δ 1Yk +Δ Yl.-δ 1Yl +Δ Ym.-δ 1Ym +Δ Yn.-
              δ1Yn

ΔP11 =     Δ Pj +Δ Pk +Δ Pl + ΔPm + ΔPn.

ΔZ11 =    Δ  Zj +Δ Zk +Δ Zl +Δ Zm + ΔZn.

1.    If Yo -α (Po -Δ Po) > 0, Y11- α(P11 -Δ P11)>
   0, and γ1(P11 -Δ P11) < (Po -Δ Po), thenΔYo = Yo -αγ 1(P11 -Δ P11) and
   ΔY11 = Y11 -α (P11 -Δ P11).
2.    If Yo - α(Po -Δ Po) > 0, Y11 -α (P11 - P11)
   > 0, and γ1(P11 -Δ P11) > (Po -Δ Po), then
   ΔYo = Yo -α (Po -Δ Po) and ΔY11 = Y11 - (α/γ1)(Po -Δ Po).
 3.    If Yo - α(Po -Δ Po) < 0, Y11 - α(P11 - P11) >
   0, and Y11 -α (P11 - P11) > Y11 - (Yo/γ1), then
   ΔYo = Yo -αγ 1(P11 -Δ P11) and Y11 = Y11 -α (P11 -Δ P11).
  4.    If Yo - α(Po -Δ Po) < 0, Y11 - (Yo/γ1) > 0, and
   Y11 - α(P11 - P11) < Y11 - (Yo/γ1), then ΔYo = 0 and ΔY11 = Y11 - (Yo/γ1).

   5.    If Y11 -α (P11 -Δ P11) < 0, Y11 - (Yo/γ1) < 0, and
   Yo - α(Po - ΔPo) < Yo - (γ1Y11), then
   ΔYo = Yo - (γ1Y11) and ΔY11 = 0.
6.    If Y11 - α(P11 - ΔP11) < 0, Yo - α(Po -Δ Po) >
   0, and Yo -α (Po -Δ Po) > Yo - (γ1Y11), then
   ΔYo = Yo - α(Po - Po) and
  ΔY11 = Y11 - (α/γ1)(Po -Δ Po).

ΔYj = δ1Yj + [(Yj -δ 1Yj )/Y11 ] ΔY11

ΔYk = δ1Yk + [(Yk - δ1Yk )/Y11 ] ΔY11

ΔYl = δ1Yl + [(Yl - δ1Yl )/Y11 ] ΔY11

ΔYm = δ1Ym + [(Ym -δ 1Ym )/Y11 ] ΔY11

ΔYn =δ 1Yn + [(Yn - δ1Yn )/Y11 ]Δ Y11

ΔYo = δ1Yo + [(Yo - δ1Yo )/Y11 ]Δ Y11

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

1.    Making the ratio of (Yo - Δ Yo ) to (Y11 - Δ Y11  ) equal to
      γ1 after taking account of the allocation  Realized Losses and the
      distributions  that  will be made  through  the end of the  Distribution
      Date to which such  provisions  relate and assuring  that the  Principal
      Reduction  Amount  for  each  of the  Class YAA,  Class YBB,  Class YCC,
      Class YDD,   Class YEE,   Class YFF,  Class ZAA,  Class ZBB,  Class ZCC,
      Class ZDD,  Class ZEE  and  Class ZFF  Certificates  is greater  than or
      equal to zero for such Distribution Date;
2.    Making the Class YAA  Principal  Balance less than or equal to 0.0005 of
      the  sum  of  the  Class YAA  and  Class ZAA  Principal  Balances,   the
      Class YBB  Principal  Balance less than or equal to 0.0005 of the sum of
      the Class YBB and Class ZBB Principal Balances,  the Class YCC Principal
      Balance  less than or equal to 0.0005  of the sum of the  Class YCC  and
      Class ZCC Principal Balances,  the Class YDD Principal Balance less than
      or equal to 0.0005 of the sum of the Class YDD  and Class ZDD  Principal
      Balances,  the Class YEE  Principal Balance less than or equal to 0.0005
      of the sum of the  Class YEE and  Class ZEE  Principal  Balances and the
      Class YFF  Principal  Balance less than or equal to 0.0005 of the sum of
      the  Class YFF  and  Class ZFF  Principal  Balances  in each case  after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
3.    Making  the  larger  of  (a)  the  fraction  whose  numerator  is  (Yo -
      ΔYo ) and whose  denominator  is the sum of (Yo -  Yo)  and
      (Zo -  Zo)  and  (b)  the  fraction  whose  numerator  is  (Y11 -
      ΔY11)  and whose  denominator is the sum of (Y11 - ΔY11) and
      (Z11 -Δ Z11)  as large as possible  while  remaining  less than or
      equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to the  related  class  of
ratio-strip principal only certificates,  if any, and (b) the remainder of the
Available  Distribution Amount for the related Pool or after reduction thereof
by the  distributions to be made on such  Distribution Date (i) to the related
class of ratio-strip principal only certificates,  if any, (ii) to the related
class of ratio-strip interest only certificates,  if any, and (iii) in respect
of interest on the related  Class Y and Class Z  Certificates,  or, if both of
such goals cannot be accomplished within such requirement,  such adjustment as
is necessary  shall be made to accomplish goal 1 within such  requirement.  In
the  event of any  conflict  among the  provisions  of the  definition  of the
Class Y Principal  Reduction  Amounts,  such conflict shall be resolved on the
basis  of  the  goals  and  their   priorities  set  forth  above  within  the
requirement  set forth in the preceding  sentence.  If the formula  allocation
ofΔ Y11 among ΔYj,  ΔYk, Δ Yl, ΔYm and ΔYn
cannot be achieved  because one or more of Δ Yj, Δ Yk,  ΔYl,
ΔYm,  and  ΔYn,  as so defined is greater  than the related one of
ΔPj,  ΔPk,Δ  Pl,Δ Pm and ΔPn, such an allocation
shall  be made as close as  possible  to the  formula  allocation  within  the
requirement  that  ΔYj <ΔPj,  ΔYk <ΔPk, Δ Yl <
ΔPl, ΔYm < ΔPm and ΔYn < ΔPn.

II.  If M%<R<N%, make the following additional definitions:

δ2Yj =  0,                                                    if R21< r21;

      Yj                                                     if R21> r21 and R21>M%;

            (R21- r21)( Yj + Yk + Yl + Ym )Yj/
            {(R21 - J%)Yj + (R21 - K%)Yk + (R21 - L%)Yl },   if R21> r21 and
      M%>R21>L%;

      (R21- r21)( Yj + Yk + Yl + Ym )Yj/
            {(R21 - J%)Yj + (R21 - K%)Yk },                  if R21> r21 and
      L%>R21>K%; and

      (R21- r21)( Yj + Yk + Yl + Ym )/(R21 - J%),            if R21> r21 and
      K%>R21>J%.

δ2Yk =  0,                                                    if R21< r21 and R21>K%;
      (R21- r21)( Yj + Yk + Yl + Ym )Yk/
            { (R21 - K%)Yk + (R21 - L%)Yl + (R21 - M%)Ym },  if R21<r21 and R21<K%;

            Yk                                               if R21>r21 and R21>M%;

           (R21- r21)( Yj + Yk + Yl + Ym )Yk/
            {(R21 - J%)Yj + (R21 - K%)Yk + (R21 - L%)Yl },   if R21>  r21 and
     M%>R21>L%;

      (R21- r21)( Yj + Yk + Yl + Ym )Yk/
            {(R21 - J%)Yj + (R21 - K%)Yk },                  if R21> r21 and
      L%>R21>K%; and

      0,                                                     if R21> r21 and R21<K%.

δ2Yl = 0,                                                     if R21< r21 and R21>L%;

            (R21- r21)( Yj + Yk + Yl + Ym )Yl/
            { (R21 - L%)Yl + (R21 - M%)Ym },                 if R21< r21 and
      K%<R21<L%;

      (R21- r21)( Yj + Yk + Yl + Ym )Yl/
            { (R21 - K%)Yk + (R21 - L%)Yl + (R21 - M%)Ym },  if R21< r21 and R21<K%;

            Yl                                               if R21> r21 and N%>R21>M%;

            (R21- r21)( Yj + Yk + Yl + Ym )Yl/
            {(R21 - J%)Yj + (R21 - K%)Yk + (R21 - L%)Yl },   if R21> r21 and
      M%>R21>L%;

      0,                                                     if R21> r21 and R21<L%.

δ2Ym = 0,                                                     if R21<r21 and R21>M%;

            (R21- r21)( Yj + Yk + Yl + Ym )/
            { (R21 - M%) },                                  if R21< r21 and L%<R21<M%;

            (R21- r21)( Yj + Yk + Yl + Ym )Ym/
            { (R21 - L%)Yl + (R21 - M%)Ym },                 if R21< r21 and
      K%<R21<L%;

      (R21- r21)( Yj + Yk + Yl + Ym )Ym/
            { (R21 - K%)Yk + (R21 - L%)Yl + (R21 - M%)Ym },  if R21< r21 and R21<K%;

            Ym                                               if R21>r21 and R21>M%;

            0,                                               if R21> r21 and R21<M%.

δ2Yn =      0,                                                if R22< r22;

      (R22- r22)( Yn + Yo )/(R22 - N%),                      if R22> r22;

 δ     2Yo =      (R22- r22)( Yn + Yo)/(R22 - O%),            if R22< r22;

            0,                                               if R22> r22.

δ2Yj,δ 2Yk,δ 2Yl, δ2Ym, δ2Yn, andδ 2Yo,
      are numbers respectively between Yj, Yk, Yl, Ym, Yn, and Yo and 0 such
      that:
            {J%(Yj - δ2Yj ) + K%( Yk.-δ 2Yk) + L%( Yl.-δ 2Yl) + M%( Ym.-δ2Ym) + }/
                   (Yj -δ 2Yj + Yk.- δ2Yk + Yl.δ- 2Yl + Ym.-δ 2Ym )
            = R21;
      and
            { N%( Yn.-δ 2Yn) + O%(Yo -δ 2Yo ) }/(Yn.-δ 2Yn + Yo -δ 2Yo)  = R22.

Y21 =       Yj -δ 2Yj + Yk.-δ 2Yk + Yl.-δ 2Yl + Ym.- δ2Ym

P21 =       Pj + Pk + Pl + Pm

Z21 =       Zj + Zk + Zl + Zm.

ΔY21 =  Δ    Yj -δ 2Yj + ΔYk.-δ 2Yk + ΔYl.-δ 2Yl + ΔYm.-δ 2Ym

 Δ     P21 =    Δ   Pj +  ΔPk +  ΔPl +  ΔPm

 ΔZ21 =      Δ Zj +  ΔZk +  ΔZl +  ΔZm.

Y22 =       Yn.- δ2Yn + Yo - δ2Yo.

P22 =       Pn + Po.

Z22 =       Zn + Zo.

ΔY22 =  Δ    Yn.- δ2Yn + ΔYo.- δ2Yo

ΔP22 =    Δ  Pn + ΔPo.

ΔZ22 = ΔZn + ΔZo.

1.    If Y22 - α(P22 -Δ P22) > 0, Y21-α (P21 -Δ P21)
   > 0, and γ2(P21 - ΔP21) < (P22 -Δ P22), then
   ΔY22 = Y22 - αγ2(P21 -Δ P21) and
   Y21 = Y21 -α (P21 -Δ P21).
2.    If Y22 -α (P22 -Δ P22) > 0,
   Y21 - α(P21 -Δ P21) > 0, and γ2(P21 -Δ P21) >
   (P22 - ΔP22), then ΔY22 = Y22 -α (P22 - ΔP22) and
   ΔY21 = Y21 - (α/γ2)(P22 - ΔP22).
3.    If Y22 - α(P22 -Δ P22) <0, Y21 -α (P21 -Δ P21)
   > 0, and Y21 - α(P21 -Δ P21)> Y21 - (Y22/γ2), then
   ΔY22 = Y22 - αγ2(P21 -ΔP21) and
   ΔY21 = Y21 - α(P21 - ΔP21).
4.    If Y22 - α(P22 - ΔP22) < 0, Y21 - (Y22/γ2) => 0, and
   Y21 - α(P21 -Δ P21) < Y21 - (Y22/γ2), then
   ΔY22 = 0 and ΔY21 = Y21 - (Y22/γ2).
5.    If Y21 - α(P21 -Δ P21) < 0, Y21 - (Y22/γ2) < 0, and
   αY22 - (P22 -ΔP22) <Y22 - (γ2Y21), then
   ΔY22 = Y22 - (γ2Y21) andΔ Y21 = 0.
6.    If Y21 - α(P21 - ΔP21) < 0, Y22 - α(P22 - ΔP22)
   > 0, and Y22 - α(P22 -Δ P22) > Y22 - (γ2Y21), then
   ΔY22 = αY22 - (P22 - ΔP22) and
   ΔY21 = Y21 - (αγ/2)(P22 - ΔP22).

ΔYj = δ2Yj + [(Yj - δ2Yj )/Y21 ] ΔY21

ΔYk = δ2Yk + [(Yk - δ2Yk )/Y21 ] ΔY21

ΔYl = δ2Yl + [(Yl - δ2Yl )/Y21 ] ΔY21

ΔYm = δ2Ym + [(Ym - δ2Ym )/Y21 ]Δ Y21

ΔYn = δ2Yn + [(Yn -δ 2Yn )/Y22 ] ΔY22

ΔYo = δ2Yo + [(Yo -δ 2Yo )/Y22 ]Δ Y22

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

1.    Making the ratio of (Y22 - Δ Y22 ) to (Y21 - ΔY21 ) equal to
      γ2 after taking account of the allocation  Realized Losses and the
      distributions  that  will be made  through  the end of the  Distribution
      Date to which such  provisions  relate and assuring  that the  Principal
      Reduction  Amount  for  each  of the  Class YAA,  Class YBB,  Class YCC,
      Class YDD,   Class YEE,   Class YFF,  Class ZAA,  Class ZBB,  Class ZCC,
      Class ZDD,  Class ZEE  and  Class ZFF  Certificates  is greater  than or
      equal to zero for such Distribution Date;
2.    Making the Class YAA  Principal  Balance less than or equal to 0.0005 of
      the  sum  of  the  Class YAA  and  Class ZAA  Principal  Balances,   the
      Class YBB  Principal  Balance less than or equal to 0.0005 of the sum of
      the Class YBB and Class ZBB Principal Balances,  the Class YCC Principal
      Balance  less than or equal to 0.0005  of the sum of the  Class YCC  and
      Class ZCC Principal Balances,  the Class YDD Principal Balance less than
      or equal to 0.0005 of the sum of the Class YDD  and Class ZDD  Principal
      Balances,  the Class YEE  Principal Balance less than or equal to 0.0005
      of the sum of the  Class YEE and  Class ZEE  Principal  Balances and the
      Class YFF  Principal  Balance less than or equal to 0.0005 of the sum of
      the  Class YFF  and  Class ZFF  Principal  Balances  in each case  after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
3.    Making  the  larger  of (a)  the  fraction  whose  numerator  is  (Y22 -
      ΔY22 ) and whose  denominator is the sum of (Y22 -Δ Y22) and
      (Z22 - Δ Z22)  and  (b) the  fraction  whose  numerator  is (Y21 -
      ΔY21)  and whose  denominator is the sum of (Y21 - ΔY21) and
      (Z21 - ΔZ21)  as large as possible  while  remaining  less than or
      equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to the  related  class  of
ratio-strip principal only certificates,  if any, and (b) the remainder of the
Available  Distribution Amount for the related Pool or after reduction thereof
by the  distributions to be made on such  Distribution Date (i) to the related
class of ratio-strip principal only certificates,  if any, (ii) to the related
class of ratio-strip interest only certificates,  if any, and (iii) in respect
of interest on the related  Class Y and Class Z  Certificates,  or, if both of
such goals cannot be accomplished within such requirement,  such adjustment as
is necessary  shall be made to accomplish goal 1 within such  requirement.  In
the  event of any  conflict  among the  provisions  of the  definition  of the
Class Y Principal  Reduction  Amounts,  such conflict shall be resolved on the
basis  of  the  goals  and  their   priorities  set  forth  above  within  the
requirement set forth in the preceding  sentence.  If the formula  allocations
of  ΔY21  among  ΔYj,  Δ Yk,  ΔYl,  and  ΔYm  or
ΔY22  among  ΔYn and ΔYo  cannot be achieved  because one or
more ofΔ Yj, Δ Yk, Δ Yl, ΔYm, ΔYn andΔ Yo,
as so  defined  is  greater  than the  related  one of  ΔPj, Δ Pk,
ΔPl, Δ Pm, Δ Pn,  and ΔPo such an allocation  shall be
made as close as  possible to the formula  allocation  within the  requirement
that  ΔYj < Δ Pj,  ΔYk < Δ Pk, Δ Yl < ΔPl,
ΔYm <Δ Pm,Δ Yn < ΔPn and ΔYo < Po.

III.  If L%<R<M%, make the following additional definitions:

δ3Yj =      0,                                               if R31< r31;

      Yj                                                    if R31> r31 and R31>L%;

            (R31- r31)( Yj + Yk + Yl )Yj/
            {(R31 - J%)Yj + (R31 - K%)Yk },                 if R31> r31 and
       L%>R31>K%; and

      (R31- r31)( Yj + Yk + Yl )/(R31 - J%),                if R31> r31 and
      K%>R31>J%.

δ3Yk =      0,                                               if R31< r31 and R31>K%;

            (R31- r31)( Yj + Yk + Yl )Yk/
            { (R31 - K%)Yk + (R31 - L%)Yl },                if R31<r31 and R31<K%;

            Yk                                              if R31> r31 and R31>M%;

            (R31- r31)( Yj + Yk + Yl )Yk/
            {(R31 - J%)Yj + (R31 - K%)Yk + (R31 - L%)Yl },  if R31> r31 and M%>R31>L%;

            (R31- r31)( Yj + Yk + Yl )Yk/
            {(R31 - J%)Yj + (R31 - K%)Yk },                 if R31> r31 and
      L%>R31>K%; and

      0,                                                    if R31> r31 and R31<K%.

δ3Yl =      0,                                               if R31< r31 and R31>L%;

            (R31- r31)( Yj + Yk + Yl )/
            { (R31 - L%) },                                 if R31< r31 and
      K%<R31<L%;

      (R31- r31)( Yj + Yk + Yl )Yl/
            { (R31 - K%)Yk + (R31 - L%)Yl },                if R31<r31 and R31<K%;

            Yl                                              if R31> r31 and M%>R31>L%;

            0,                                              if R31> r31 and R31<L%.

δ3Ym =      0,                                               if R32<r32;

      (R32- r32)( Ym + Yn + Yo )Ym/{ (R32 - M%)Ym           if R32> r32 and R32>N%;
           + (R32 - N%)Yn },

      (R32- r32)( Ym + Yn + Yo )/ (R32 - M%),               if R32> r32 and
      N%>R32>M%;

δ3Yn =      0,                                               if R32< r32 and R32>N%;

            (R32- r32)( Ym + Yn + Yo)Yn/{ (R32 - N%)Yn +    if R32< r32 and M%<R32<N%;
            (R32 - O%)Yo },

            (R32- r32)( Ym + Yn + Yo )Yn/{ (R32 - M%)Ym +   if R32> r32 and R32>N%;
            (R32 - N%)Yn },

      0,                                                    if R32> r32 and R32<P%.

δ3Yo =      (R32- r32)( Ym + Yn + Yo )/(R32 - O%),           if R32< r32 and P%<R32;

           (R32- r32)( Ym + Yn + Yo )Yo/{ (R32 - N%)Yn +    if R32<r32 and M%<R32<N%;
           (R32 - O%)Yo },

      0,                                                    if R32> r32.

δ3Yj, δ3Yk,δ 3Yl, δ3Ym,δ 3Yn and δ3Yo are
      numbers respectively between Yj, Yk, Yl, Ym, Yn and Yo and 0 such that:
            {J%(Yj -δ 3Yj ) + K%( Yk.- δ3Yk) + L%( Yl.-
      δ3Yl) )}/
                  (Yj -δ 3Yj + Yk.-δ 3Yk + Yl.-δ 3Yl )
            = R31;
      and
            { M%( Ym.-δ 3Ym) + N%( Yn.-δ 3Yn) + O%(Yo -
      δ3Yo ) }/( Ym.- δ3Ym + Yn.- δ3Yn + Yo -δ 3Yo)
            = R32.

ΔY31 =      Δ Yj - δ3Yj + ΔYk.- δ3Yk + ΔYl.- δ3Yl

ΔP31 =      Δ Pj + ΔPk + ΔPl

ΔZ31 =      ΔZj + ΔZk + ΔZl

Y31 =      Yj - δ3Yj + Yk.-δ 3Yk +
      Yl.- δ3Yl

P31 =      Pj + Pk + Pl .

Z31 =      Zj + Zk + Zl

ΔY32 =      Δ Ym.- δ3Ym +Δ Yn.- δ3Yn + ΔYo - δ3Yo.

ΔP32 =       ΔPm + ΔPn +Δ Po.

ΔZ32 =       ΔZm + ΔZn + ΔZo.

Y32 =      Ym.- 3Ym + Yn.- 3Yn +
      Yo.- 3Yo

P32 =      Pm + Pn + Po.

Z32 =      Zm + Zn + Zo.

1.    If Y32 - α(P32 -Δ P32) > 0, Y31-α (P31 -Δ P31)
   > 0, and γ3(P31 - ΔP31) < (P32 -Δ P32), then
   ΔY32 = Y32 - αγ3(P31 -Δ P31) and
   Y31 = Y31 -α (P31 -Δ P31).
2.    If Y32 -α (P32 -Δ P32) > 0,
   Y31 - α(P31 -Δ P31) > 0, and γ3(P31 -Δ P31) >
   (P32 - ΔP32), then ΔY32 = Y32 -α (P32 - ΔP32) and
   ΔY31 = Y31 - (α/γ3)(P32 - ΔP32).
3.    If Y32 - α(P32 -Δ P32) <0, Y31 -α (P31 -Δ P31)
   > 0, and Y31 - α(P31 -Δ P31)> Y31 - (Y32/γ2), then
   ΔY32 = Y32 - αγ3(P31 -ΔP31) and
   ΔY31 = Y31 - α(P31 - ΔP31).
4.    If Y32 - α(P32 - ΔP32) < 0, Y31 - (Y32/γ3) => 0, and
   Y31 - α(P31 -Δ P31) < Y31 - (Y32/γ3), then
   ΔY32 = 0 and ΔY31 = Y31 - (Y32/γ3).
5.    If Y31 - α(P31 -Δ P31) < 0, Y31 - (Y32/γ3) < 0, and
   αY32 - (P32 -ΔP32) <Y32 - (γ3Y31), then
   ΔY32 = Y32 - (γ2Y21) andΔ Y31 = 0.
6.    If Y31 - α(P31 - ΔP31) < 0, Y32 - α(P32 - ΔP32)
   > 0, and Y32 - α(P32 -Δ P32) > Y32 - (γ3Y31), then
   ΔY32 = αY32 - (P32 - ΔP32) and
   ΔY31 = Y31 - (αγ/3)(P32 - ΔP32).

ΔYj = δ3Yj + [(Yj - δ3Yj )/Y31 ] ΔY31

ΔYk = δ3Yk + [(Yk - δ3Yk )/Y31 ] ΔY31

ΔYl = δ3Yl + [(Yl - δ3Yl )/Y31 ] ΔY31

ΔYm = δ3Ym + [(Ym - δ3Ym )/Y32 ]Δ Y32

ΔYn = δ3Yn + [(Yn -δ 3Yn )/Y32 ] ΔY32

ΔYo = δ3Yo + [(Yo -δ 3Yo )/Y32 ]Δ Y32

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

1.    Making the ratio of (Y32 - Δ Y32 ) to (Y31 - Y31 ) equal to
      3 after taking account of the allocation  Realized Losses and the
      distributions  that  will be made  through  the end of the  Distribution
      Date to which such  provisions  relate and assuring  that the  Principal
      Reduction  Amount  for  each  of the  Class YAA,  Class YBB,  Class YCC,
      Class YDD,   Class YEE,   Class YFF,  Class ZAA,  Class ZBB,  Class ZCC,
      Class ZDD,  Class ZEE  and  Class ZFF  Certificates  is greater  than or
      equal to zero for such Distribution Date;
2.    Making the Class YAA  Principal  Balance less than or equal to 0.0005 of
      the  sum  of  the  Class YAA  and  Class ZAA  Principal  Balances,   the
      Class YBB  Principal  Balance less than or equal to 0.0005 of the sum of
      the Class YBB and Class ZBB Principal Balances,  the Class YCC Principal
      Balance  less than or equal to 0.0005  of the sum of the  Class YCC  and
      Class ZCC Principal Balances,  the Class YDD Principal Balance less than
      or equal to 0.0005 of the sum of the Class YDD  and Class ZDD  Principal
      Balances,  the Class YEE  Principal Balance less than or equal to 0.0005
      of the sum of the  Class YEE and  Class ZEE  Principal  Balances and the
      Class YFF  Principal  Balance less than or equal to 0.0005 of the sum of
      the  Class YFF  and  Class ZFF  Principal  Balances  in each case  after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
3.    Making  the  larger  of (a)  the  fraction  whose  numerator  is  (Y32 -
      Δ Y32 ) and whose  denominator is the sum of (Y32 -Δ  Y32) and
      (Z32 - Δ  Z32)  and  (b) the  fraction  whose  numerator  is (Y31 -
      Δ Y31)  and whose  denominator is the sum of (Y31 -Δ  Y31) and
      (Z31 - Δ Z31)  as large as possible  while  remaining  less than or
      equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to the  related  class  of
ratio-strip principal only certificates,  if any, and (b) the remainder of the
Available  Distribution Amount for the related Pool or after reduction thereof
by the  distributions to be made on such  Distribution Date (i) to the related
class of ratio-strip principal only certificates,  if any, (ii) to the related
class of ratio-strip interest only certificates,  if any, and (iii) in respect
of interest on the related  Class Y and Class Z  Certificates,  or, if both of
such goals cannot be accomplished within such requirement,  such adjustment as
is necessary  shall be made to accomplish goal 1 within such  requirement.  In
the  event of any  conflict  among the  provisions  of the  definition  of the
Class Y Principal  Reduction  Amounts,  such conflict shall be resolved on the
basis  of  the  goals  and  their   priorities  set  forth  above  within  the
requirement set forth in the preceding  sentence.  If the formula  allocations
of Δ Y31  among  Δ Yj,  Δ Yk andΔ Yl or Δ Y32  among
Δ Ym, Δ  Yn and Δ Yo  cannot be achieved because one or more of
Δ Yj,  Δ Yk, and Δ Yl,  Δ Ym, and Δ Yo, as so defined
is  greater  than  the  related  one  of Δ  Pj,  Δ  Pk, Δ   Pl,
Δ Pm, Δ  Pn,  and  Δ Po,  such an  allocation  shall be made as
close as  possible  to the  formula  allocation  within the  requirement  that
Δ Yj  < Δ  Pj,  Δ  Yk  < Δ  Pk,  Δ  Yl  <  Δ Pl,
Δ Ym < Δ Pm, Δ Yn < Δ Pn and Δ Yo < Δ Po

IV.  If K%<R<L%, make the following additional definitions:

δ4Yj =      0,                                               if R41< r41;

      Yj                                                    if R41> r41 and L%>R41>K%;
      and

      (R41- r41)( Yj + Yk )/(R41 - J%),                     if R41> r41 and K%>R41>J%.

      4Yk =      0,                                         if R41< r41 and R41>K%;

            (R41- r41)( Yj + Yk )/
            { (R41 - K%) },                                 if R41<r41 and R41<K%;

            Yk                                              if R41> r41 and L%>R41>K%; and

            0,                                              if R41>r41 and R41<K%.

δ4Yl =      0,                                               if R42<r42;

      (R42- r42)( Yl + Ym + Yn + Yo )Yl/
            { (R42 - L%)Yl + (R42 - M%)Ym + (R42 - N%)Yn }, if R42> r42 and R42>N%;

            (R42- r42)( Yl + Ym + Yn + Yo )Ym/
            { (R42 - L%)Yl + (R42 - M%)Ym },                if R42> r42 and N%>R42>M%;

            (R42- r42)( Yl + Ym + Yn + Yo )/(R42 - L%),     if R42> r42 and M%>R42>L%;

            0,                                              if R42> r42 and R42<N%.

δ4Ym =      0,                                               if R42<r42 and R42>M%;

            (R42- r42)( Yl + Ym + Yn + Yo )Ym/
            { (R42 - M%)Ym + (R42 - N%)Yn + (R42 - O%)Yo }, if R42< r42 and N%<R42<M%;

            (R42- r42)( Yl + Ym + Yn + Yo )Ym/
            { (R42 - L%)Yn + (R42 - M%)Ym + (R42 - N%)Yn }, if R42> r42 and R42>N%;

            (R42- r42)( Yl + Ym + Yn + Yo )Ym/
            { (R42 - L%)Yl + (R42 - M%)Ym},                 if R42> r42 and N%>R42>M%;

            0,                                              if R42> r42 and R42<M%.

δ4Yn =      0,                                               if R42<r42 and R42>N%;

            (R42- r42)( Yl + Ym + Yn + Yo )Yn/
            { (R42 - N%)Yn + (R42 - O%)Yo},                 if R42<r42 and M%<R42<N%;

            (R42- r42)( Yl + Ym + Yn + Yo)Yn/
            { (R42 - M%)Ym + (R42 - N%)Yp + (R42 - O%)Yo }, if R42< r42 and L%<R42<M%;

            (R42- r42)( Yl + Ym + Yn + Yo )Yn/
            { (R42 - L%)Yl + (R42 - M%)Ym + (R42 - N%)Yn }, if R42> r42 and R42>N%;

            0,                                              if R42> r42 and R42<N%.

δ4Yo =      (R42- r42)( Yl + Ym + Yn + Yo )/(R42 - O%),
                                                            if R42< r42 and N%<R42;

      (R42- r42)( Yl + Ym + Yn + Yo)Yo/
            { (R42 - N%)Yn + (R42 - O%)Yo },                if R42< r42 and M%<R42<N%;

            (R42- r42)( Yl + Ym + Yn + Yo)Yo/
            { (R42 - M%)Ym + (R42 - N%)Yn + (R42 - O%)Yo }, if R42<r42 and N%<R42<O%;

            0,                                              if R42> r42.

δ4Yj, δ4Yk, δ4Yl, δ4Ym, and δ4Yo are numbers
      respectively between Yj, Yk, Yl, Ym, Yn, and Yo and 0 such that:
            {J%(Yj - δ4Yj ) + K%( Yk.-δ 4Yk )}/
                  ( Yj - δ4Yj + Yk.-δ 4Yk )
            = R41;
      and
            { L%( Yl.- δ4Yl) + M%( Ym.- δ4Ym) + N%( Yn.-
      δ4Yn) + O%(Yo - δ4Yo ) }/
                  (Yl.- δ4Yl + Ym.- δ4Ym + Yn.- δ4Yn + Yo -
      4Yo)
            = R42.

Y41 =       Yj -δ 4Yj + Yk.-δ 4Yk

P41 =       Pj + Pk.

Z41 =       Zj + Zk.

ΔY41 =     Δ Yj -Δ 4Yj + ΔYk.- Δ4Yk

ΔP41 =     Δ Pj + ΔPk

ΔZ41 =      ΔZj +Δ Zk

Y42 =       Yl.- δ4Yl + Ym.- δ4Ym + Yn.- δ4Yn + Yo -
     δ 4Yo.

P42 =       Pl + Pm + Pn + Po.

Z42 =       Zl + Zm + Zn + Zo.

ΔY42 =      ΔYl.- δ4Yl + ΔYm.-δ 4Ym +
      ΔYn.- δ4Yn + ΔYo.-δ 4Yo

ΔP42 =     Δ Pl +Δ Pm + ΔPn + ΔPo.

ΔZ42 =     Δ Zl +Δ Zm +Δ Zn + ΔZo.

1.    If Y42 - α(P42 -Δ P42) > 0, Y41- α(P41 -Δ P41)
   > 0, and γ4(P41 - ΔP41) < (P42 - ΔP42), then
   ΔY42 = Y42 - αγ4(P41 -Δ P41) and
   ΔY41 = Y41 - α(P41 -Δ P41).
2.    If Y42 - α(P42 - ΔP42) > 0,
   Y41 - α(P41 - ΔP41) >0, and γ4(P41 -Δ P41) >
   (P42 -Δ P42), then ΔY42 = Y42 -α (P42 - P42) and
  ΔY41 = Y41 - (α/γ4)(P42 -Δ P42).
3.    If Y42 - α(P42 -Δ P42) < 0, Y41 - α(P41 -Δ P41)
   > 0, and Y41 - α(P41 -Δ P41) > Y41 - (Y42/γ4), then
   ΔY42 = Y42 -αγ 4(P41 - P41Δ) and
   Y41 = Y41 - α(P41 -Δ P41).
4.    If Y42 - α(P42 -Δ P42) < 0, Y41 - (Y42/γ4) >; 0, and
   Y41 - α(P41 -Δ P41) < Y41 - (Y42/γ4), then
   ΔY42 = 0 and ΔY41 = Y41 - (Y42/γ4).
5.    If Y41 - α(P41 - ΔP41) < 0, Y41 - (Y42/γ4) < 0, and
   Y42 - α(P42 -Δ P42) < Y42 - (γ4Y41), then
   ΔY42 = Y42 - (γ4Y41) andΔ Y41 = 0.
6.    If Y41 - α(P41 - ΔP41) <0, Y42 - α(P42 -Δ P42)
   > 0, and Y42 - α(P42 - ΔP42) >Y42 - (γ4Y41), then
   ΔY42 = Y42 - α(P42 -Δ P42) and
   ΔY41 = Y41 - (α/γ4)(P42 -Δ P42).

ΔYj = δ4Yj + [(Yj -δ 4Yj )/Y41 ] ΔY41

ΔYk = δ4Yk + [(Yk - δ4Yk )/Y41 ] ΔY41

ΔYl = δ4Yl + [(Yl - δ4Yl )/Y42 ] ΔY42

ΔYm = δ4Ym + [(Ym - δ4Ym )/Y42 ]Δ Y42

ΔYn = δ4Yn + [(Yn - δ4Yn )/Y42 ]Δ 42

ΔYo = δ4Yo + [(Yo - δ4Yo )/Y42 ]Δ Y42

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

1.    Making the ratio of (Y42 -  ΔY42 ) to (Y41 - ΔY41 ) equal to
      γ4 after taking account of the allocation  Realized Losses and the
      distributions  that  will be made  through  the end of the  Distribution
      Date to which such  provisions  relate and assuring  that the  Principal
      Reduction  Amount  for  each  of the  Class YAA,  Class YBB,  Class YCC,
      Class YDD,   Class YEE,   Class YFF,  Class ZAA,  Class ZBB,  Class ZCC,
      Class ZDD,  Class ZEE  and  Class ZFF  Certificates  is greater  than or
      equal to zero for such Distribution Date;
2.    Making the Class YAA  Principal  Balance less than or equal to 0.0005 of
      the  sum  of  the  Class YAA  and  Class ZAA  Principal  Balances,   the
      Class YBB  Principal  Balance less than or equal to 0.0005 of the sum of
      the Class YBB and Class ZBB Principal Balances,  the Class YCC Principal
      Balance  less than or equal to 0.0005  of the sum of the  Class YCC  and
      Class ZCC Principal Balances,  the Class YDD Principal Balance less than
      or equal to 0.0005 of the sum of the Class YDD  and Class ZDD  Principal
      Balances,  the Class YEE  Principal Balance less than or equal to 0.0005
      of the sum of the  Class YEE and  Class ZEE  Principal  Balances and the
      Class YFF  Principal  Balance less than or equal to 0.0005 of the sum of
      the  Class YFF  and  Class ZFF  Principal  Balances  in each case  after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
3.    Making  the  larger  of (a)  the  fraction  whose  numerator  is  (Y42 -
      ΔY42 ) and whose  denominator is the sum of (Y42 -Δ Y42) and
      (Z42 -Δ  Z42)  and  (b) the  fraction  whose  numerator  is (Y41 -
     Δ Y41)  and whose  denominator is the sum of (Y41 - ΔY41) and
      (Z41 - ΔZ41)  as large as possible  while  remaining  less than or
      equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to the  related  class  of
ratio-strip principal only certificates,  if any, and (b) the remainder of the
Available  Distribution Amount for the related Pool or after reduction thereof
by the  distributions to be made on such  Distribution Date (i) to the related
class of ratio-strip principal only certificates,  if any, (ii) to the related
class of ratio-strip interest only certificates,  if any, and (iii) in respect
of interest on the related  Class Y and Class Z  Certificates,  or, if both of
such goals cannot be accomplished within such requirement,  such adjustment as
is necessary  shall be made to accomplish goal 1 within such  requirement.  In
the  event of any  conflict  among the  provisions  of the  definition  of the
Class Y Principal  Reduction  Amounts,  such conflict shall be resolved on the
basis  of  the  goals  and  their   priorities  set  forth  above  within  the
requirement set forth in the preceding  sentence.  If the formula  allocations
ofΔY41  among Δ Yj,  and ΔYk or ΔY42 among ΔYl,
ΔYm,  ΔYn and ΔYo  cannot be achieved because one or more of
ΔYj,  ΔYk,  ΔYl,  ΔYm, ΔYn, and ΔYo, as so
defined is greater than the related one of  ΔPj,  ΔPk,  ΔPl,
ΔPm,  ΔPn,  and  ΔPo,  such an  allocation  shall be made as
close as  possible  to the  formula  allocation  within the  requirement  that
ΔYj <Δ Pj, Δ Yk <Δ Pk, ΔYl <Δ Pl,Δ Ym
<Δ Pm,Δ Yn < ΔPn and ΔYo <Δ Po.

V.  If R<K%, make the following additional definitions:

δ5Yj =      0,

δ5Yk =      0,                                                    if R52< r52;

      (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yk/
            { (R52 - K%)Yk + (R52 - L%)Yl +
            (R52 - M%)Ym + (R52 - N%)Yn },                       if R52>r52 and R52>N%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yk/
            { (R52 - K%)Yk + (R52 - L%)Yl + (R52 - M%)Ym},       if R52> r52 and N%>R52>M%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yk/
            { (R52 - K%)Yk + (R52 - L%)Yl },                     if R52>r52 and M%>R52>L%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )/(R52 - K%),     if R52> r52 and N%>R52>M%;

 δ     5Yl =      0,                                              if R52< r52 and R52>N%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yl/
            { (R52 - L%)Yl + (R52 - M%)Ym +
            (R52 - N%)Yn + (R52 - O%)Yo },                       if R52< r52 and K%<R52<L%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yl/
            { (R52 - K%)Yk + (R52 - L%)Yl +
            (R52 - M%)Ym + (R52 - N%)Yn },                       if R52> r52 and R52>N%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yl/
            { (R52 - K%)Yk + (R52 - L%)Yl + (R52 - M%)Ym },      if R52> r52 and N%>R52>M%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yl/
            { (R52 - K%)Yk + (R52 - L%)Yl },                     if R52> r52 and K%>R52>L%;

            0,                                                   if R52> r52 and R52<L%.

δ5Ym =      0,                                                    if R52< r52 and R52>O%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Ym/
            { (R52 - M%)Ym + (R52 - N%)Yn + (R52 - O%)Yo },      if R52< r52 and L%<R52<M%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Ym
            { (R52 - L%)Yl + (R52 - M%)Ym + (R52 - N%)Yn +
            (R52 - O%)Yo },                                      if R52<r52 and K%<R52<L%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Ym/
            { (R52 - K%)Yk + (R52 - L%)Yl +
            (R52 - M%)Ym + (R52 - N%)Yn },                       if R52> r52 and R52>N%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Ym/
            { (R52 - K%)Yk + (R52 - L%)Yl + (R52 - M%)Ym},       if R52> r52 and N%>R52>M%;

            0,                                                   if R52> r52 and R52<M%.

δ5Yn =      0,                                                    if R52<r52 and R52>P%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yn/
            { (R52 - N%)Yn + (R52 - O%)Yo },                     if R52< r52  and M%<R52<N%;

           (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yn/
            { (R52 - M%)Ym + (R52 - N%)Yn + (R52 - O%)Yo },      if R52<r52 and L%<R52<M%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yn/
            { (R52 - L%)Yl + (R52 - M%)Ym + (R52 - N%)Yn +
            (R52 - O%)Yo },                                      if R52< r52 and K%<R52<L%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo )Yn/
            { (R52 - K%)Yk + (R52 - L%)Yl +
            (R52 - M%)Ym + (R52 - N%)Yn },                       if R52> r52 and R52>N%;

            0,                                                   if R52>r52 and R52<N%.

δ5Yo =      (R52- r52)( Yk + Yl + Ym + Yn + Yo)/(R52 - O%),
                                                                 if R52< r52 and N%<R52;

      (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yo/
            { (R52 - N%)Yn + (R52 - O%)Yo },                     if R52< r52 and M%<R52<N%;

            (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yo/
            { (R52 - M%)Ym + (R52 - N%)Yn + (R52 - O%)Yo },      if R52<r52 and L%<R52<M%;

           (R52- r52)( Yk + Yl + Ym + Yn + Yo)Yo/
            { (R52 - L%)Yl + (R52 - M%)Ym + (R52 - N%)Yn +
            (R52 - O%)Yo },                                      if R52< r52 and K%<R52<L%;

            0,                                                   if R52>r52.

δ5Yj,δ 5Yk, δ5Yl,δ 5Ym,δ5Yn, and δ5Yo
      are numbers respectively between Yj, Yk, Yl, Ym, Yn, and Yo, and 0 such
      that:
            {J%(Yj - δ5Yj )}/
                  ( Yj -δ 5Yj )
            = R51;
      and
            { K%( Yk.-δ 5Yk) + L%( Yl.- δ5Yl) + M%( Ym.-
      δ5Ym) + N%( Yn.-δ 5Yn) + O%(Yo - δ5Yo ) }/
                  (Yk.- δ5Yk + Yl.-δ 5Yl + Ym.- δ5Ym + Yn.-
      δ5Yn + Yo - δ5Yo)
            = R52.

Y51 =       Yj - δ5Yj

P51 =       Pj

Z51 =       Zj

ΔY51 =      Yj - δ5Yj

ΔP51 =     Δ Pj

ΔZ51 =      ΔZj

Y52 =       Yk.- δ5Yk + Yl.-δ 5Yl + Ym.- δ5Ym + Yn.-
      δ5Yn + Yo -δ 5Yo.

P52 =       Pk + Pl + Pm + Pn + Po.

Z52 =       Zk + Zl + Zm + Zn + Zo.

ΔY52 =   Δ   Ym.-δ 5Ym + ΔYn.-δ 5Yn + Yo.-
      δ5Yo + ΔYp.- δ5Yp + ΔYq.-δ 5Yq

ΔP52 =    Δ  Pm + ΔPn +Δ Po + ΔPp +Δ Pq.

ΔZ52 =     Δ Zm + ΔZn + ΔZo + ΔZp + ΔZq.

1.    If Y52 - α(P52 - ΔP52) > 0, Y51- α(P51 - ΔP51)
   > 0, and γ5(P51 -Δ P51) <(P52 -Δ P52), then
   ΔY52 = Y52 - αγ5(P51 -Δ P51) and
  Δ Y51 = Y51 - α(P51 - ΔP51).
2.    If Y52 - α(P52 - ΔP52) > 0,
   αY51 - (P51 -Δ P51) > 0, and γ5(P51 - ΔP51) >
   (P52 -Δ P52), thenΔ Y52 = Y52 -α (P52 -Δ P52) and
   ΔY51 = Y51 - (α/γ5)(P52 - ΔP52).
3.    If Y52 - (αP52 - ΔP52) < 0, Y51 - α(P51 -Δ P51)
   >0, and Y51 - α(P51 - ΔP51) > Y51 - (Y52/γ5), then
   ΔY52 = Y52 -αγ 5(P51 - ΔP51) and
   ΔY51 = Y51 - α(P51 -Δ P51).
4.    If Y52 - α(P52 -Δ P52) <0, Y51 - (Y52/γ5) >0, and
   Y51 - α(P51 - ΔP51) < Y51 - (Y52/γ5), then
   ΔY52 = 0 and ΔY51 = Y51 - (Y52/γ5).
5.    If Y51 - α(P51 - ΔP51) < 0, Y51 - (Y52/γ5) < 0, and
   Y52 - α(P52 - ΔP52) < Y52 - (γ5Y51), then
   ΔY52 = Y52 - (γ5Y51) and ΔY51 = 0.
6.    If Y51 - -(P51 -ΔP51) < 0, Y52 - α(P52 - ΔP52)
   > 0, and Y52 - α(P52 - ΔP52)> Y52 - (γ5Y51), then
   ΔY52 = Y52 - α(P52 -Δ P52) and
   Y51 = Y51 - (α/γ5)(P52 -Δ P52).

ΔYj = Y51

ΔYk = δ5Yk + [(Yk -δ 5Yk )/Y51 ]Δ Y52

ΔYl = δ5Yl + [(Yl - δ5Yl )/Y51 ]Δ Y52

ΔYm =δ 5Ym + [(Ym -δ 5Ym )/Y52 ] ΔY52

ΔYn = δ5Yn + [(Yn -δ 5Yn )/Y52 ] ΔY52

ΔYo = δ5Yo + [(Yo -δ 5Yo )/Y52 ] ΔY52

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

1.    Making the ratio of (Y52 - Δ Y52  ) to (Y51 - Δ Y51  ) equal
      to γ5 after taking account of the allocation  Realized  Losses and
      the distributions  that will be made through the end of the Distribution
      Date to which such  provisions  relate and assuring  that the  Principal
      Reduction  Amount  for  each  of the  Class YAA,  Class YBB,  Class YCC,
      Class YDD,   Class YEE,   Class YFF,  Class ZAA,  Class ZBB,  Class ZCC,
      Class ZDD,  Class ZEE  and  Class ZFF  Certificates  is greater  than or
      equal to zero for such Distribution Date;
2.    Making the Class YAA  Principal  Balance less than or equal to 0.0005 of
      the  sum  of  the  Class YAA  and  Class ZAA  Principal  Balances,   the
      Class YBB  Principal  Balance less than or equal to 0.0005 of the sum of
      the Class YBB and Class ZBB Principal Balances,  the Class YCC Principal
      Balance  less than or equal to 0.0005  of the sum of the  Class YCC  and
      Class ZCC Principal Balances,  the Class YDD Principal Balance less than
      or equal to 0.0005 of the sum of the Class YDD  and Class ZDD  Principal
      Balances,  the Class YEE  Principal Balance less than or equal to 0.0005
      of the sum of the  Class YEE and  Class ZEE  Principal  Balances and the
      Class YFF  Principal  Balance less than or equal to 0.0005 of the sum of
      the  Class YFF  and  Class ZFF  Principal  Balances  in each case  after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
3.    Making  the  larger  of (a)  the  fraction  whose  numerator  is  (Y52 -
      ΔY52 ) and whose  denominator is the sum of (Y52  -ΔY52) and
      (Z52 - Δ Z52)  and  (b) the  fraction  whose  numerator  is (Y51 -
      ΔY51)  and whose  denominator is the sum of (Y51 - ΔY51) and
      (Z51 - ΔZ51)  as large as possible  while  remaining  less than or
      equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to the  related  class  of
ratio-strip principal only certificates,  if any, and (b) the remainder of the
Available  Distribution Amount for the related Pool or after reduction thereof
by the  distributions to be made on such  Distribution Date (i) to the related
class of ratio-strip principal only certificates,  if any, (ii) to the related
class of ratio-strip interest only certificates,  if any, and (iii) in respect
of interest on the related  Class Y and Class Z  Certificates,  or, if both of
such goals cannot be accomplished within such requirement,  such adjustment as
is necessary  shall be made to accomplish goal 1 within such  requirement.  In
the  event of any  conflict  among the  provisions  of the  definition  of the
Class Y Principal  Reduction  Amounts,  such conflict shall be resolved on the
basis  of  the  goals  and  their   priorities  set  forth  above  within  the
requirement set forth in the preceding  sentence.  If the formula  allocations
of ΔY52  among  ΔYk,  ΔYl,  and  ΔYm,  ΔYn,  and
ΔYo  cannot be  achieved  because  one or more of Δ Yj,  ΔYk,
ΔYl,  ΔYm, Δ Yn and ΔYo, as so defined is greater than
the related one of  ΔPj,  ΔPk, Δ Pl, ΔPm,  ΔPn,
and Δ Po,  such an allocation  shall be made as close as possible to the
formula   allocation  within  the  requirement  that Δ Yj  < Δ Pj,
ΔYk  < Δ Pk,  Δ Yl  <Δ  Pl, Δ  Ym  < Δ Pm,
ΔYn <ΔPn andΔ Yo < ΔPo.

      (2) For any  Distribution  Date  the  amounts  by  which  the  principal
balances of the  Class Y7A  and Class Y7B  Certificates  respectively  will be
reduced on such  distribution  date by the  allocation of Realized  Losses and
the distribution of principal, determined as follows:

First  for each of  Group 5A  and  Group 5B  determine  the  weighted  average
pass-through  rate for that Group for  distributions  of interest that will be
made on the next succeeding  Distribution  Date (the "Group  Interest  Rate").
The Principal  Reduction Amount for each of the Class Y  Certificates  will be
determined  pursuant  to the  "Generic  solution  for  the  Class Y  Principal
Reduction  Amounts"  set  forth  below  (the  "Generic  Solution")  by  making
identifications  among the actual Groups and their related Class Y and Class Z
Certificates and weighted average  pass-through  rates and the Groups named in
the Generic  Solution and their related  Class Y and Class Z  Certificates  as
follows:

A. Determine  which Group has the lower Group  Interest Rate.  That Group will
be identified with Group AA and the Class Y and Class Z  Certificates  related
to  that  Group  will  be  respectively  identified  with  the  Class YAA  and
Class ZAA  Certificates.  The  Group  Interest  Rate  for that  Group  will be
identified  with J%. If the two Groups have the same Group  Interest Rate pick
one for this  purpose,  subject  to the  restriction  that  each  Group may be
picked only once in the course of any such  selections  pursuant to paragraphs
A and B of this definition.

B. Determine  which Group has the higher Group Interest Rate.  That Group will
be identified with Group BB and the Class Y and Class Z  Certificates  related
to that Group will be respectively  identified with the Class BB and Class ZBB
Certificates.  The Group Interest Rate for that Group will be identified  with
K%.  If the two  Groups  have the same  Group  Interest  Rate  the  Group  not
selected  pursuant to  paragraph  A, above,  will be selected  for purposes of
this paragraph B.

Second,  apply the Generic  Solution set forth below to determine  the Class Y
Principal   Reduction   Amounts   for  the   Distribution   Date   using   the
identifications made above.

Generic Solution for the Class Y Principal Reduction Amounts:

For any Distribution  Date, the amounts by which the principal balances of the
Class YAA  and  Class YBB  Certificates  respectively  will be reduced on such
Distribution  Date by the allocation of Realized  Losses and the  distribution
of principal, determined as follows:

J%  and  K%  represent   the   interest   rates  on  Group  AA  and  Group  BB
respectively.  J%<K%.

For purposes of the succeeding  formulas the following  symbols shall have the
meanings set forth below:

PJB =       the Group AA Subordinate  Balance after the allocation of Realized
      Losses and distributions of principal on such Distribution Date.

PKB = the Group BB  Subordinate  Balance  after  the  allocation  of  Realized
      Losses and distributions of principal on such Distribution Date.

R =   the Class CB Pass Through Rate = (J%PJB + K%PKB)/(PJB + PKB)

Yj =  the  Class YAA  Principal  Balance  after  distributions  on  the  prior
      Distribution Date.

Yk =  the  Class YBB  Principal  Balance  after  distributions  on  the  prior
      Distribution Date.

ΔYj =       the Class YAA Principal Reduction Amount.

ΔYk =       the Class YBB Principal Reduction Amount.

Zj =  the  Class ZAA  Principal  Balance  after  distributions  on  the  prior
      Distribution Date.

Zk =  the  Class ZBB  Principal  Balance  after  distributions  on  the  prior
      Distribution Date.

ΔZj =       the Class ZAA Principal Reduction Amount.

ΔZk =       the Class ZBB Principal Reduction Amount.

Pj =  the  aggregate  Class  Principal  Balance of the Class YAA and Class ZAA
      Regular Interests after  distributions on the prior  Distribution  Date,
      which is equal to the aggregate  principal balance of the Group AA Loans
      reduced  by the  Group AA Class P  principal  balance,  if any,  and the
      Class R Principal Balance, if applicable.

Pk =  the  aggregate  Class  Principal  Balance of the Class YBB and Class ZBB
      Regular Interests after  distributions on the prior  Distribution  Date,
      which is equal to the aggregate  principal balance of the Group BB Loans
      reduced by the Group BB Class P  principal  balance,  if any and Class R
      Principal Balance, if applicable.

ΔPj = the aggregate  principal  reduction resulting on such Distribution
      Date on the  Group  AA  Loans as a  result  of  principal  distributions
      (exclusive  of any amounts  distributed  pursuant  to clauses  (c)(i) or
      (c)(ii) of the  definition  of REMIC I  Distribution  Amount) to be made
      and realized losses to be allocated on such Distribution  Date,  reduced
      by the  portion,  if any, of such  reduction  allocable  to any Group AA
      Class P Certificates or the Class R Certificates,  if applicable,  which
      is equal to the  aggregate  of the  Class YAA  and  Class ZAA  Principal
      Reduction Amounts.

ΔPk=  the aggregate  principal  reduction resulting on such Distribution
      Date on the  Group  BB  Loans as a  result  of  principal  distributions
      (exclusive  of any amounts  distributed  pursuant  to clauses  (c)(i) or
      (c)(ii) of the  definition  of REMIC I  Distribution  Amount) to be made
      and realized losses to be allocated on such Distribution  Date,  reduced
      by the  portion,  if any, of such  reduction  allocable  to any Group BB
      Class P Certificates or the Class R Certificates,  if applicable,  which
      is equal to the  aggregate  of the  Class YBB  and  Class ZBB  Principal
      Reduction Amounts.

α =   .0005

γ =   (R - J%)/(K% - R).  γ is a  non-negative  number  unless its
      denominator is zero, in which event it is undefined.

If γ is zero, ΔYk = Yk and ΔYj = (Yj/Pj)ΔPj.

If γ is undefined, ΔYj = Yj, ΔYk = (Yk/Pk)ΔPk.

In the  remaining  situations,  ΔYk  and Δ Yj  shall be defined as
      follows:

7.    If Yk - α(Pk - ΔPk) > 0, Yj-  α(Pj - ΔPj)>0,
   and       γ (Pj    -    Δ Pj)     <    (Pk    -    Δ Pk),
   ΔYk = Yk -            αγ  (Pj - ΔPj)            and
  Δ Yj = Yj - α(Pj -Δ Pj).
8.    If  Yk - α(Pk -Δ Pk)  > 0,  Yj - α(Pj -ΔPj) >
   0,     and         γ  (Pj -Δ Pj)      >      (Pk - ΔPk),
   ΔYk = Yk -α (Pk -Δ Pk)                                and
   ΔYj = Yj - (α/γ)(Pk - ΔPk).
9.    If Yk - α(Pk -Δ Pk) < 0,  Yj - α(Pj - ΔPj) > 0,
   and        Yj - α(Pj - ΔPj)        >       Yj - (Yk/γ),
   ΔYk = Yk -              αγ(Pj -Δ Pj)            and
   ΔYj = Yj - α(Pj -Δ Pj).
10.   If   Yk - α(Pk -Δ Pk) <0,    Yj - (Yk/γ) >0,    and
   Yj - α(Pj -Δ Pj) < Yj - (Yk/γ),    Δ Yk = 0    and
   ΔYj = Yj - (Yk/γ).
11.   If    Yj -α (Pj -Δ Pj) < 0,    Yj - (Yk/γ) < 0,    and
   Yk - α(Pk -Δ Pk) < Yk - (γYj),
   ΔYk = Yk - (γYj) and ΔYj = 0.
12.   If Yj - α(Pj -ΔPj) < 0,  Yk - α(Pk -ΔPk) > 0,
   and         Yk - α(Pk - ΔPk)        >        Yk - (γYj),
   ΔYk = Yk - α(Pk - ΔPk)                                and
   ΔYj = Yj - (α/γ)(Pk - ΔPk).

The  purpose  of the  foregoing  definitional  provisions  together  with  the
related  provisions  allocating  Realized  Losses and defining the Class Y and
Class Z  Principal  Distribution  Amounts is to accomplish the following goals
in the following order of priority:

4.    Making the ratio of Yk to Yj equal to   after  taking  account of
      the allocation  Realized Losses and the distributions  that will be made
      through end of the  Distribution  Date to which such  provisions  relate
      and  assuring  that  the  Principal  Reduction  Amount  for  each of the
      Class YAA,  Class YBB,  Class ZAA and Class ZBB  Certificates is greater
      than or equal to zero for such Distribution Date;
5.    Making (i) the Class YAA  Principal Balance less than or equal to 0.0005
      of the sum of the Class YAA and  Class ZAA  Principal  Balances and (ii)
      the Class YBB  Principal Balance less than or equal to 0.0005 of the sum
      of the  Class YBB and  Class ZBB  Principal  Balances in each case after
      giving effect to allocations of Realized Losses and  distributions to be
      made through the end of the  Distribution  Date to which such provisions
      relate; and
6.    Making the larger of (a) the  fraction  whose  numerator is Yk and whose
      denominator  is  the  sum  of Yk  and Zk  and  (b)  the  fraction  whose
      numerator is Yj and whose  denominator is the sum of Yj, and Zj as large
      as possible while remaining less than or equal to 0.0005.

In the  event of a failure  of the  foregoing  portion  of the  definition  of
ClassY  Principal  Reduction Amount to accomplish both of goals 1 and 2 above,
the  amounts  thereof  should be adjusted  to so as to  accomplish  such goals
within the requirement  that each Class Y  Principal  Reduction Amount must be
less  than or  equal to the sum of (a) the  Principal  Realized  Losses  to be
allocated  on the related  Distribution  Date for the related  Pool  remaining
after  the  allocation  of  such  Realized  Losses  to  the  related  Class  P
Certificates  and (b) the remainder of the Available  Distribution  Amount for
the related Pool or after reduction  thereof by the  distributions  to be made
on such  Distribution  Date (i) to the related Class P  Certificates,  (ii) to
the  related  Class X  Certificates  and (iii) in respect of  interest  on the
related Class Y and Class Z Certificates,  or, if both of such goals cannot be
accomplished  within such  requirement,  such adjustment as is necessary shall
be made to  accomplish  goal 1 within  such  requirement.  In the event of any
conflict  among the  provisions  of the  definition  of the Class Y  Principal
Reduction  Amounts,  such conflict shall be resolved on the basis of the goals
and their  priorities set forth above within the  requirement set forth in the
preceding sentence.