Document:

<PAGE>
                                                             Exhibit 10.15

                     AMENDMENT NO. 3 TO OPTION AGREEMENT II

* Portions of this document have been omitted and filed separately with the
Securities and Exchange Commission pursuant to a request for confidential
treatment.

                                    AMENDMENT

This Amendment No. 3 to Option Agreement II (the "Amendment No. 3") is effective
as of June 16, 2000 (the "Effective Date") by and between Adaptec Manufacturing
(S) Pte. Ltd., a company organized under the laws of Singapore, with its current
registered address at 6 Battery Road, 532-00, Singapore 049909 ("Customer"), and
Taiwan Semiconductor Manufacturing Co., Ltd., a company organized under the laws
of the Republic of China, with its registered address at No. 121 Park Avenue 3,
Science-Based Industrial Park, Hsin-Chu, Taiwan, Republic of China ("TSMC"), for
the purpose of amending the Option Agreement II entered into by Customer and
TSMC on October 23, 1995 (the "Option Agreement II") as follows:

1.       Replace Section 7(a) with the followings:

         "The term of this Agreement  shall  commence from the Effective  Date,
         and continue until December 31, 2004."

2.       Add the followings at Section 20:

         "Section 20       Non-Publicity

         (a) No publicity or information regarding the existence or contents of
         this Agreement shall be given or released by either party in any case,
         other than as required by law. In the event that any applicable law or
         regulation  requires the disclosure of this Agreement,  the disclosing
         party  must  provide  details  of  the  disclosure  request  prior  to
         submission of such information to the requesting authority.

         (b) The  exchange of  information  by either party for the purposes of
         review  of the  contents  prior  to  disclosure  as  described  in the
         foregoing  Section  20(a)  will be  handled  directly  by the TSMC and
         Customer    representatives    responsible   for   official    company
         communications and public relations:

         For TSMC

         Name:                      Ronald C. Norris
         Title:                     Senior Vice President, Worldwide Marketing
                                    and Sales
         Address:                   No. 121, Park Avenue 3, Science-Based
                                    Industrial Park, Hsin-Chu,
                                    Taiwan, Republic of China
         Telephone No:              011-886-3-578-0221
         Fax No:                    011-886-3-578-1545

                                    Cc to:

         Name:                      David Keller
         Title:                     Senior Director, Account Management, TSMC NA
         Address:                   1740 Technology Drive, Suite 660, San Jose,
                                    CA 95110, USA
         Telephone No:              408-487-4139
         Fax No:                    408-441-7713

         For Customer

                                       1
<PAGE>

         Name:                      Dolores Marciel
         Title:                     Vice President of Worldwide Material
         Address:                   691 South Milpitas Boulevard, Milpitas,
                                    CA 95035, USA
         Telephone No:              408-945-8600
         Fax No:                    408-957-8227

         (c) In the event that  either  party  breaches  Section  20(a) of this
         Agreement,  the  non-breaching  party  may  terminate  this  Agreement
         immediately  with a 180 days  written  notice to the  breaching  party
         pursuant to Section 7(c) of this Agreement."

3.       Replace Exhibits B and D with the new Exhibits B and D attached hereto.

4.       Customer  agrees to pay to TSMC in cash the entire  Option Fee for the
         year 2003 and 2004,  total in the amount of US$20,000,000 as set forth
         in the new Exhibit D, by June 16, 2000.

5.       All the other terms and  conditions  of the Option  Agreement  II shall
         remain  unchanged  to the  extent  not in  conflict  with the terms and
         conditions in this Amendment No. 3.

Taiwan Semiconductor                        Adaptec Manufacturing (S) Pte. Ltd.
Manufacturing Co., Ltd.

/s/ Ronald C. Norris                        /s/ Kok Yong Lim
------------------------------------        ------------------------------------
Name:    Ronald C. Norris                   Name:    Kok Yong Lim
Title:   Senior Vice President              Title:   Vice President
         Worldwide Marketing & Sales                 Manufacturing

                                       2
<PAGE>

                                    Exhibit B
                        CUSTOMER/TSMC COMMITTED CAPACITY

                           Unit: K 6" Wafer Equivalent

<TABLE>
<CAPTION>
                                                     2000       2001       2002       2003       2004
                                                     ----       ----       ----       ----       ----
<S>                                                  <C>        <C>        <C>        <C>        <C>

Base Capacity                                        [*]        [*]        [*]        [*]        [*]
(For Options)

X% of Base                                           [*]        [*]        [*]        [*]        [*]
Capacity

Option                                               [*]        [*]        [*]        [*]        [*]

TSMC Committed Capacity                              [*]        [*]        [*]        [*]        [*]
(Base Capacity + Option Capacity)

Customer Committed Capacity                          [*]        [*]        [*]        [*]        [*]
(X% Base Capacity + Option Capacity)

</TABLE>

Option Capacity [*] wafers times [*] per wafer = US $33.6 Million for years 1999
- 2002
Option Capacity [*] wafers times [*] per wafer = US $20 Million for years 2003
and 2004

[*]  Confidential  information  has been omitted and filed  separately  with the
Securities  and  Exchange  Commission  pursuant  to a request  for  confidential
treatment.

                                       3
<PAGE>

                                    Exhibit D
                                   OPTION FEE

<TABLE>
<CAPTION>
Year          Option Capacity                    Option Fee                     Due Date
              (Unit: Wafer Equivalent)           (Unit: US$)
----------------------------------------------------------------------------------------------
<S>           <C>                                <C>                            <C>
2000          [*]                                $8.4M                          Paid

2001          [*]                                $8.4M                          Paid

2002          [*]                                $8.4M                          Paid

2003          [*]                                $10M                           June 16, 2000

2004          [*]                                $10M                           June 16, 2000

</TABLE>

[*]  Confidential  information  has been omitted and filed  separately  with the
Securities  and  Exchange  Commission  pursuant  to a request  for  confidential
treatment.

                                       4<PAGE>

                                                                    EXHIBIT 10.1

                     DYNAMICS RESEARCH CORPORATION PLACES
                        $10 MILLION LONG TERM FINANCING

Andover, MA - June 21, 2000 - Dynamics Research Corporation (Nasdaq:DRCO) today
announced that it has placed a $10 million ten-year mortgage facility on the
Company's real estate with Brown Brothers Harriman & Co. and Banknorth Group,
Inc. Proceeds from the loan were used to repay $7.5 million of interim mortgage
financing that was obtained in February 2000. The balance of the proceeds was
used to repay outstanding debt on the company's revolving credit agreement.

"This long-term financing significantly strengthens the company's capital
structure and better positions us to support future operational requirements,"
said James P. Regan, president and chief executive officer.

Dynamics Research Corporation is an innovative solutions provider that partners
with its customers in government and commercial sectors to apply proven
processes and technologies. DRC delivers engineering, logistics, and information
technology services and precision manufactured products that enhance the
performance and cost effectiveness of its customers' mission critical systems

Safe harbor statement under the Private Securities Litigation Reform Act of
1995: Information statements contained in this news release which are not
historical fact such as expectations as to future revenues, involve uncertainty.
Such statements are subject to various factors, including uncertainties
regarding actual future customer requirements, exercise of contractual options
and government funding actions that could cause actual results to differ
materially from those set forth in the forward looking statements. These factors
are discussed in more detail in the Company's Annual Report on Form 10-K for the
year ended December 31, 1999.<PAGE>

                                                                    EXHIBIT 10.2

                SECOND AMENDMENT TO LOAN AND SECURITY AGREEMENT
                         DATED FEBRUARY 10, 2000 AMONG
            DYNAMICS RESEARCH CORPORATION, DRC ENCODER, INC., DRC
        METRIGRAPHICS, INC., DRC SOFTWARE, INC., AND DRC TELECOM, INC.
                                      AND
       BROWN BROTHERS HARRIMAN & CO., AS ADMINISTRATIVE AGENT AND AS A
    LENDER, AND FIRST MASSACHUSETTS BANK, N.A., f/k/a FAMILY BANK, FSB, AS
                       COLLATERAL AGENT AND AS A LENDER

     This Second Amendment to Loan and Security Agreement (hereinafter, the
"Amendment") is made as of the 12th day of June, 2000 by and between Dynamics
                               --
Research Corporation, DRC Encoder, Inc., DRC Metrigraphics, Inc., DRC Software,
Inc., and DRC Telecom, Inc., Massachusetts corporations with their principal
executive offices at 60 Frontage Road, Andover, Massachusetts (hereinafter,
individually and collectively, jointly and severally,  the "Borrowers") and
Brown Brothers Harriman & Co., as administrative agent and as a lender, and
First Massachusetts Bank, N.A., f/k/a Family Bank, FSB, as collateral agent and
as a lender (hereinafter, individually and collectively, the "Lenders"), in
consideration of the mutual covenants contained herein and the benefits to be
derived herefrom. Unless otherwise specified herein, all capitalized terms shall
have the same meaning as set forth in the Loan Agreement (as defined
hereinbelow).

                             W I T N E S S E T H:
                             -------------------

     WHEREAS, the Borrowers executed and delivered to the Lenders a certain Loan
and Security Agreement dated February 10, 2000,as amended by a certain Amendment
to Loan and Security Agreement dated as of March 31, 2000 (hereinbefore and
hereinafter, as amended, the "Loan Agreement") pursuant to which, among other
things, the Lenders extended in favor of the Borrowers a Revolving Credit in the
original maximum principal amount of $20,000,000.00 and a Term Loan in the
original maximum principal amount of $7,500,000.00; and

     WHEREAS, the Borrowers have requested that the Lenders (i) increase the
Term Loan from $7,500,000.00 to $10,000,000.00, (ii) amend the repayment terms
and conditions of the Term Loan,  and (iii) otherwise modify the Loan Agreement
as set forth herein; and

     WHEREAS, the Lenders have indicated their willingness to do so, BUT ONLY on
                                                                     --------
the terms and conditions contained in this Amendment; and

     WHEREAS, the Borrowers have determined that this Amendment is in the
Borrowers' respective best interests.

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

     1.   The Borrowers hereby certify to the Lenders that, to the best of the
Borrowers' knowledge and belief after due inquiry, the representations and
warranties contained in the Loan Agreement, as modified by this Amendment, are
true as of the date hereof and that no Event of Default under the Loan Agreement
or any document executed in connection therewith has occurred and is continuing.

     2.   The definition of "Base" set forth in Article 1 of the Loan Agreement
is hereby amended to also mean and refer to "Base Rate".
<PAGE>

     3.   The definition of "Base Margin Loan" set forth in Article 1 of the
Loan Agreement is hereby deleted in its entirety and replaced with the
following:

          "Base Margin Loan": Any Revolving Credit Loan  or any portion of the
          Term Loan bearing interest at the Base Rate."

     4.   The definition of "LIBOR Loan" set forth in Article 1 of the Loan
Agreement is hereby deleted in its entirety and replaced with the following:

          "LIBOR Loan": Any Revolving Credit Loan or any portion of the Term
          Loan bearing interest at the LIBOR Rate"

     5.   The definition of "LIBOR Margin" set forth in Article 1 of the Loan
Agreement is hereby deleted in its entirety and replaced with the following:

          "LIBOR Margin": (a) As to any Revolving Credit Loan, two hundred (200)
          basis points; and (b) as to the Term Loan, two hundred fifty (250)
          basis points."

     6.   Article 1 of the Loan Agreement is hereby amended to add the following
definition of "Loan" after the definition of "Line Fee Percentage".

          "Loan": Any loan or advance made under the Revolving Credit or the
          Term Loan"."

     7.   The definition of "Loan Documents" set forth in Article 1 of the Loan
Agreement is hereby deleted in its entirety and replaced with the following:

          "This Agreement, the Revolving Credit Note, the Term Note, and each
          instrument and document executed and/or delivered as contemplated by
          Article 6 below, and each other instrument or document from time to
          time executed and/or delivered in connection with the arrangements
          contemplated hereby, as each may be amended from time to time."

     8.   The definition of "Maturity Date" set forth in Article 1 of the Loan
Agreement is hereby deleted in its entirety and replaced with the following:

          "Maturity Date": (a) As to the Revolving Credit Loans, February 10,
          2003; and (b) as to the Term Loan, May 1, 2010."

     9.   Section 3-10(a) of the Loan Agreement is hereby amended by deleting
the following text:

          "(a) Subject to the limitation described herein, and provided the
          LIBOR Condition has been satisfied, the Lead Borrower shall have the
          option to elect an Interest Period applicable to a Revolving Credit
          Loan by giving notice of such election (a "Renewal/Conversion Notice")
          in the form of EXHIBIT 3-10,",

and the following substituted therefor:

          "(a) Subject to the limitations described herein, the Lead Borrower
          shall have the option to elect an Interest Period to be applicable to
          a

                                      -2-
<PAGE>

          Revolving Credit Loan or any portion of the Term Loan by giving
          notice of such election (a "Renewal/Conversion Notice") in the form of
          EXHIBIT 3-10,"

     10.  Section 3-10 (c) of the Loan Agreement is hereby deleted in its
entirety and replaced with the following:

          "(c) The Lead Borrower shall not select, renew, or convert any
          Revolving Credit Loan or any portion of the Term Loan such that there
          are more than six (6) interest rates applicable to the Revolving
          Credit Loans and Term Loan in the aggregate which are LIBOR Loans at
          any one time."

     11.  Section 3-11(b)(i) of the Loan Agreement is hereby amended to add the
following text after the words "Revolving Credit Loan":

          "or any portion of the Term Loan".

     12.  Section 3-11(b)(ii) of the Loan Agreement is hereby deleted in its
entirety and replaced with the following:

          "(ii) the indices on which the interest rates for LIBOR Loans shall no
          longer represent the effective cost to the Lenders for U.S. dollar
          deposits in the interbank market for deposits in which they regularly
          participate:

then, in any such event, the Administrative Agent shall forthwith so notify the
Lead Borrower thereof.  Until the Administrative Agent notifies the Lead
Borrower that the circumstances giving rise to such notice no longer apply, the
obligation of the Lenders to make LIBOR Loans of the type affected by such
changed circumstances or to permit the Lead Borrower to select the affected
interest rate as otherwise applicable to any Revolving Credit Loans or any
portion of the Term Loan shall be suspended.  If at any time the Administrative
Agent so notifies the Lead Borrower, the Lead Borrower has previously given the
Administrative Agent a Renewal/Conversion Notice with respect to one or more
LIBOR  Loans, but such LIBOR Loans have not gone into effect, such notification
shall be deemed to be void and the Lead Borrower may only borrow Base Margin
Loans and shall furnish a substitute Renewal/Conversion Notice in connection
therewith.  Upon the expiration of the Interest Period for any LIBOR Loan which
is outstanding on the date of such notification, the amount of such LIBOR Loan
shall thereafter constitute a Base Margin Loan."

     13.  Section 3-13(d) of the Loan Agreement is hereby amended by adding the
following clause at the end of Section 3-13 (d):

          ", plus on or before June 12, 2000, an additional fee of $20,000.00 to
                                    --
          be shared pro rata by the Lenders."

     14.  Article 4 of the Loan Agreement is hereby deleted in its entirety and
replaced with the following:

          "4-1. The Term Loan Subject to, and in accordance with this Agreement,
                -------------
          and upon satisfaction of all conditions precedent set forth in Article
          6, below, the Lender shall provide a term loan facility in the
          aggregate maximum principal sum of $10,000,000.00 (the "Term Loan") to
          the Borrowers in exchange for, and repayable with interest

                                      -3-
<PAGE>

          as provided herein and in the Borrowers' Amended and Restated Term
          Notes (hereinafter, collectively, the "Term Note") substantially in
          the form of EXHIBIT 4-1, annexed hereto.

          4-2 Interest Payments on Term Loan.
              ------------------------------

          (a) At the Lead Borrower's option and in accordance with the terms of
          this Agreement, the Term Loan shall bear interest at the Base Rate or
          the LIBOR Rate, as specified from time to time by the Lead Borrower in
          the Renewal/ Conversion Notice with respect to any portion of the Term
          Loan or as otherwise provided in this Agreement;

          (b) Interest on the Term Loan shall be payable in  arrears on the
          applicable Interest Payment Date for that Loan; and

          (c) All of the terms and conditions relating to LIBOR Loans set forth
          in this Agreement, including, without limitation, the provisions of
          Section 3-10, 3-11 and 3-12 shall be applicable to any portion of the
          Term Loan bearing interest at the LIBOR Rate."

     15.  Exhibit 1 of the Loan Agreement is hereby deleted in its entirety and
replaced with Exhibit 1 annexed hereto and specifically incorporated by
reference herein.

     16.  Exhibit 4-1 is hereby deleted in its entirety and replaced with
Exhibit 4-1 annexed hereto and specifically incorporated by reference herein.

     17.  This Amendment and all other documents, instruments or agreements
executed in connection herewith incorporate all discussions and negotiations
between the Borrowers and the Lenders, either expressed or implied, concerning
the matters included herein, any statute, custom, or usage to the contrary
notwithstanding. No such discussions or negotiations shall limit, modify or
otherwise affect the provisions hereof. No modification, amendment, or waiver of
any provision of this Amendment or the Loan Agreement or any provision under any
other agreement, document or instrument between the Borrowers and the Lenders
shall be effective unless executed in writing by the party to be charged with
such modification, amendment or waiver, and if such party be the Lenders, then
by a duly authorized officer of each Lender.

     18.  Except as specifically modified herein, the Loan Agreement shall
remain in full force and effect as originally written and the Borrowers hereby
ratify and confirm all terms and conditions contained therein and further ratify
and reaffirm all representations and warranties made therein as of the date
hereof.

     19.  This Amendment shall be construed in accordance with and governed by
the laws of the Commonwealth of Massachusetts and shall take effect as a sealed
instrument.

                                      -4-
<PAGE>

     IN WITNESS WHEREOF, the parties have hereunto set their hands and seals as
of the date first written above.

                                       DYNAMICS RESEARCH CORPORATION

                                By: /s/ David Keleher
                                    ----------------------------------------

                                Title: Chief Financial Officer
                                       -------------------------------------
                                       DRC ENCODER, INC.

                                By: /s/ David Keleher
                                    ----------------------------------------

                                Title: Chief Financial Officer
                                       -------------------------------------

                                       DRC METRIGRAPHICS, INC.

                                By: /s/ David Keleher
                                    ----------------------------------------

                                Title: Chief Financial Officer
                                       -------------------------------------

                                       DRC SOFTWARE, INC.

                                By: /s/ David Keleher
                                    ----------------------------------------

                                Title: Chief Financial Officer
                                       -------------------------------------

                                       DRC TELECOM, INC.

                                By: /s/ David Keleher
                                     ---------------------------------------

                                Title: Chief Financial Officer
                                       -------------------------------------

ACKNOWLEDGED AND AGREED:

BROWN BROTHERS HARRIMAN & CO.,
as administrative agent and as a lender

By: /s/ Timothy T. Telman
    -------------------------------------

Name: Timothy T. Telman
      -----------------------------------

Title: Vice President
       ----------------------------------

                                      -5-
<PAGE>

FIRST MASSACHUSETTS BANK, f/k/a
FAMILY BANK, FSB,
as collateral agent and as a lender

By: /s/ C. Lee Willingham
    --------------------------------------

Name:  C. Lee Willingham
       -----------------------------------

Title:  Vice President
        ----------------------------------

                                      -6-
<PAGE>

                                                                    EXHIBIT 10.2

                                   EXHIBIT 1

LENDER                         REVOLVING COMMITMENT      TERM COMMITMENT
                               /PERCENTAGE                   /PERCENTAGE

BROWN BROTHERS                     $10,000,000.00/ 50%      $5,000,000.00/ 50%
HARRIMAN & CO.

FIRST MASSACHUSETTS                $10,000,000.00/ 50%      $5,000,000.00/ 50%
BANK, N.A., formerly known as
FAMILY BANK, FSB

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