FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT


        This FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT 
AGREEMENT (this "Amendment") is entered into as of October 9, 1997, by and 
among KOMAG, INCORPORATED, a Delaware corporation ("Borrower"), the 
banks from time to time party thereto, together with their respective
successors and  assigns (each a "Bank" and collectively the "Banks"), and
BANKBOSTON, N.A., a  national banking association ("BankBoston"), as agent
for the Banks (in such  capacity, the "Agent"), with reference to the
following facts:

        A.      The Borrower, the Banks, and the Agent are parties to that
certain  Amended and Restated Credit Agreement dated as of June 20, 1997,
by and among  the Borrower, the Banks, and the Agent (the "Credit
Agreement").  The Credit  Agreement and all related and supporting
documents collectively are referred to in  this Amendment as the "Loan
Documents."

        B.      The parties desire to amend certain provisions contained in
the Credit  Agreement as set forth below.

        NOW, THEREFORE, in consideration of the promises and the
agreements,  provisions and covenants herein contained, the parties hereto
agree as follows:

        1.      Defined Terms.  Capitalized terms not otherwise defined
herein shall  have the same meanings as set forth in the Credit Agreement.

        2.      Amendments to Credit Agreement.  The Credit Agreement is
hereby  amended as follows:

                (a)     The following defined term shall be added to
Section 1.1 in its  proper alphabetical order:

                "'Net Profit Margin': Net income for any fiscal month of
Borrower,  divided by net sales for such fiscal month, excluding equity in
net income or  loss of Asahi Komag Co., Ltd."

                (b)     Section 2.1(c) is hereby amended to read as follows
from and  after the effective date of this Amendment:

                "Facility Fee.  Borrower agrees to pay to the Agent, for
the pro rata  benefit of the Banks in accordance with their respective
Commitment  Percentages, a facility fee based on the Aggregate Commitment
at the  following rates, each of which shall be calculated on the basis of
a 360-day  year for the actual days elapsed beginning on the Closing Date,
payable in  arrears at the end of each calendar quarter following the
Closing Date.  Said  rates shall be calculated quarterly based on
Borrower's performance for the  immediately preceding quarter for which
Borrower has provided information  to the Agent regarding the calculation
of the rate and shall be effective five (5)  Business Days following the
Agent's receipt of such financial statements and  the officer's certificate
required to be delivered in connection therewith  pursuant to Section
6.1(a); provided that if Borrower shall not have timely  delivered its
financial statements in accordance with Section 6.1(a) (after  giving
effect to any grace period set forth in Section 7.1(c)), then commencing 
on the date upon which such financial statements should have been delivered
 and continuing until such financial statements are actually delivered, it
shall  be assumed for purposes of determining said rates that Borrower's 
Consolidated Funded Debt to Consolidated Capital is equal to or greater
than  .25 to 1.0.

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the facility fee shall be 20 basis
points per annum; 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the facility  fee shall be 25 basis points per annum; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the facility fee shall be
30 basis  points per annum;

        provided, that upon Borrower's achievement of a cumulative average
Net  Profit Margin for any fiscal six (6) month period commencing on or
after  August 25, 1997 of at least five percent (5%), as demonstrated by
Borrower's  consolidated balance sheet for itself and its Consolidated
Subsidiaries as at the  end of such fiscal six (6) month period and the
related consolidated statements  of income, stockholders' equity and
statement of cash flows for such fiscal six  (6) month period, which
statements are certified by a duly authorized officer  of Borrower as being
fairly stated in all material respects subject to year end  adjustments,
the facility fee shall be reduced to the following rates: 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the facility fee shall be 17.5 basis
points per  annum; 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the facility  fee shall be 22.5 basis points per annum; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the facility fee shall be
27.5 basis  points per annum;

        provided, further, that upon Borrower's achievement of a cumulative
average  Net Profit Margin for any fiscal six (6) month period commencing
on or after  August 25, 1997 of at least ten percent (10%), as demonstrated
by Borrower's  consolidated balance sheet for itself and its Consolidated
Subsidiaries as at the  end of such fiscal six (6) month period and the
related consolidated statements  of income, stockholders' equity and
statement of cash flows for such fiscal six  (6) month period, which
statements are certified by a duly authorized officer  of Borrower as being
fairly stated in all material respects subject to year end  adjustments,
the facility fee shall be further reduced to the following rates: 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the facility fee shall be 15 basis
points per annum; 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the facility  fee shall be 20 basis points per annum; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the facility fee shall be
25 basis  points per annum.

        For purposes of this Section 2.1(c), Borrower shall be required to
furnish its  fiscal six (6) month financial statements only for those
periods as are  necessary to demonstrate achievement of the Net Profit
Margin tests specified  in this Section."

                (c)     Section 2.3(c) is amended to read as follows from
and after the  effective date of this Amendment:

                        "LIBOR Rate Loans.  Revolving Loans which are LIBOR
Rate  Loans shall bear interest for each Interest Period with respect
thereto on the  unpaid principal amount thereof at a rate per annum equal
to the LIBOR Rate  determined for such Interest Period plus an amount (the
"Applicable Margin")  determined in accordance with following schedule. 
Said rates shall be  calculated quarterly based on Borrower's performance
for the immediately  preceding fiscal quarter for which Borrower has
provided information to the  Agent regarding the calculation of the rate
and shall be effective five (5)  Business Days following the Agent's
receipt of such financial statements and  the officer's certificate
required to be delivered in connection therewith  pursuant to Section
6.1(a); provided that if Borrower shall not have timely  delivered its
financial statements in accordance with Section 6.1(a) (after  giving
effect to any grace period set forth in Section 7.1(c)), then commencing 
on the date upon which such financial statements should have been delivered
 and continuing until such financial statements are actually delivered, it
shall  be assumed for purposes of determining said rates that Borrower's 
Consolidated Funded Debt to Consolidated Capital is equal to or greater
than  .25 to 1.0 (said calculations shall apply to existing as well as new
LIBOR Rate  Loans).

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the Applicable Margin shall be 85 basis
points;

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the  Applicable Margin shall be 92.5 basis points; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the Applicable Margin
shall be 100  basis points;

        provided, that upon Borrower's achievement of a cumulative average
Net  Profit Margin for any fiscal six (6) month period commencing on or
after  August 25, 1997 of at least five percent (5%), as demonstrated by
Borrower's  consolidated balance sheet for itself and its Consolidated
Subsidiaries as at the  end of such fiscal six (6) month period and the
related consolidated statements  of income, stockholders' equity and
statement of cash flows for such fiscal six  (6) month period, which
statements are certified by a duly authorized officer  of Borrower as being
fairly stated in all material respects subject to year end  adjustments,
the Applicable Margin shall be as follows: 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the Applicable Margin shall be 60 basis
points;

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the  Applicable Margin shall be 67.5 basis points; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the Applicable Margin
shall be 75  basis points;

        provided, further, that upon Borrower's achievement of a cumulative
average  Net Profit Margin for any fiscal six (6) month period commencing
on or after  August 25, 1997 of at least ten percent (10%), as demonstrated
by Borrower's  consolidated balance sheet for itself and its Consolidated
Subsidiaries as at the  end of such fiscal six (6) month period and the
related consolidated statements  of income, stockholders' equity and
statement of cash flows for such fiscal six  (6) month period, which
statements are certified by a duly authorized officer  of Borrower as being
fairly stated in all material respects subject to year end  adjustments,
the Applicable Margin shall be as follows: 

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  less than .15 to 1.0:  the Applicable Margin shall be 35 basis
points;

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .15 to 1.0 but less than .25 to 1.0: 
the  Applicable Margin shall be 42.5 basis points; and

                If Borrower's Consolidated Funded Debt to Consolidated
Capital is  equal to or greater than .25 to 1.0:  the Applicable Margin
shall be 50  basis points.

        For purposes of this Section 2.3(c), Borrower shall be required to
furnish its  fiscal six (6) month period financial statements only for
those periods as are  necessary to demonstrate achievement of the Net
Profit Margin tests specified  in this Section."

                (d)     Section 6.2(a) is amended to read as follows:

                        "Profitability.  Permit, on a consolidated
after-tax basis, (i) an  aggregate net loss for the period beginning
September 29, 1997 and ending  March 31, 1998 of more than Twenty Million
Dollars ($20,000,000); or (ii) a  net loss in any two consecutive fiscal
quarter periods commencing after  December 28, 1997."

        3.      Conditions to Effectiveness.

                This Amendment shall become effective as of October 9, 1997
(the  "Closing Date"), only upon:

                (i) receipt by the Agent from the Borrower of a fee equal
to One  Hundred Thousand Dollars ($100,000), to be distributed to the Banks
on a pro rata  basis in accordance with the respective Commitment
Percentage of each Bank; 

                (ii)    receipt by the Agent of the following (each of
which shall be in  form and substance satisfactory to the Agent and its
counsel, with sufficient copies for  each of the Banks):  counterparts of
this Amendment duly executed on behalf of the  Borrower, the Agent, and the
Majority Banks.

        4.      Representations and Warranties.  In order to induce the
Banks to enter  into this Amendment, the Borrower represents and warrants
to the Agent and each  Bank that the following statements are true, correct
and complete as of the effective  date of this Amendment:

                (a)     Corporate Power and Authority.  The Borrower has
all  requisite corporate power and authority to enter into this Amendment
and to carry out  the transactions contemplated by, and perform its
obligations under, the Credit  Agreement as amended by this Amendment (the
"Amended Agreement").  The  Certificate of Incorporation and Bylaws of the
Borrower have not been amended since  the copies previously delivered to
the Agent or Banks.  

                (b)     Authorization of Agreements.  The execution and
delivery of  this Amendment and the performance by the Borrower of the
Amended Agreement  have been duly authorized by all necessary corporate
action on the part of the  Borrower.  

                (c)     No Conflict.  The execution and delivery by the
Borrower of  this Amendment do not and will not contravene (i) any law or
any governmental rule  or regulation applicable to the Borrower, (ii) the
Certificate of Incorporation or  Bylaws of the Borrower, (iii) any order,
judgment or decree of any court or other  agency of government binding on
the Borrower, or (iv) any material agreement or  instrument binding on the
Borrower. 

                (d)     Governmental Consents.  The execution and delivery
by the  Borrower of this Amendment and the performance by the Borrower of
the Amended  Agreement do not and will not require any registration with,
consent or approval of,  or notice to, or other action to, with or by, any
federal, state or other governmental  authority or regulatory body.

                (e)     Binding Obligation.  This Amendment and the Amended
Agreement have been duly executed and delivered by the Borrower and are the
binding obligations of the Borrower, enforceable against the Borrower in
accordance  with their respective terms, except in each case as such
enforceability may be limited  by bankruptcy, insolvency, reorganization,
liquidation, moratorium or other similar  laws and equitable principles
relating to or affecting creditors' rights.

                (f)     Incorporation of Representations and Warranties
From Credit  Agreement.  The representations and warranties contained in
Section 5.1 of the Credit  Agreement are correct on and as of the effective
date of this Amendment as though  made on and as of such date (except to
the extent such representations and warranties  expressly refer to an
earlier date, in which case they were true and correct as of such  earlier
date and except that Section 5.1(e) shall be deemed instead to refer to the
last  day of the most recent fiscal year and fiscal quarter for which
financial statements  have then been delivered).

                (g)     Absence of Default.  No event has occurred and is
continuing  or will result from the consummation of the transactions
contemplated by this  Amendment that would constitute an Event of Default
or a Potential Event of Default. 

        5.      Miscellaneous.

                (a)     Reference to and Effect on the Credit Agreement and
the Other  Loan Documents.  

                        (i)     On and after the Closing Date, each
reference in the  Credit Agreement to "this Agreement", "hereunder",
"hereof", "herein" or words of  like import referring to the Credit
Agreement, and each reference in the other Loan  Documents to the "Credit
Agreement," "thereunder", "thereof" or words of like  import referring to
the Credit Agreement, shall mean and be a reference to the  Amended
Agreement. 

                        (ii)    Except as specifically amended by this
Amendment, the  Credit Agreement and the other Loan Documents shall remain
in full force and effect  and are hereby ratified and confirmed.  

                        (iii)   The execution, delivery and performance of
this  Amendment shall not, except as expressly provided herein, constitute
a waiver of any  provision of, or operate as a waiver of any right, power
or remedy of the Agent or any  Bank under the Credit Agreement or any of
the other Loan Documents. 

                (b)     Fees and Expenses.  All reasonable and documented
costs and  expenses of the Agent, including, but not limited to, reasonable
and documented  attorneys' fees, incurred by the Agent in the preparation
and implementation of this  Amendment constitute costs and expenses in
connection with the amendment and  restructuring of the Loan Documents, and
as such are payable by the Borrower in  accordance with Section 9.5 of the
Credit Agreement.  

                (c)     Headings.  Section and subsection headings in this
Amendment  are included herein for convenience of reference only and shall
not constitute a part of  this Amendment for any other purpose or be given
any substantive effect. 

                (d)     Applicable Law.  THIS AMENDMENT SHALL BE  GOVERNED
BY, AND SHALL BE CONSTRUED AND ENFORCED IN  ACCORDANCE WITH, THE INTERNAL
LAWS OF THE STATE OF  CALIFORNIA, WITHOUT REGARD TO CONFLICTS OF LAWS
PRINCIPLES.

                (e)     Counterparts.  This Amendment may be executed in
any  number of counterparts and by different parties hereto in separate
counterparts, each  of which when so executed and delivered shall be deemed
an original, but all such  counterparts together shall constitute but one
and the same instrument; signature  pages may be detached from multiple
separate counterparts and attached to a single  counterpart so that all
signature pages are physically attached to the same document. 

        IN WITNESS WHEREOF, the parties hereto have caused this Agreement
to  be executed by their respective officers thereunto duly authorized, as
of the date first  above written.

KOMAG, INCORPORATED


By:                                             
Title:                                          


BANKBOSTON, N.A., 
as the Agent and as a Bank


By:                                             
Title:                                          


COMERICA BANK - CALIFORNIA, 
as a Bank

By:                                             
Title:                                          


STANDARD CHARTERED BANK, 
as a Bank

By:                                             
Title:                                          

By:                                             
Title:                                          

BANQUE NATIONALE DE PARIS, 
as a Bank

By:                                                     
Title:                                          

By:                                             
Title:                                          


FLEET NATIONAL BANK, 
as a Bank

By:                                             
Title:                                          


BANK OF MONTREAL, as a Bank

By:                                             
Title:                                          


THE BANK OF NOVA SCOTIA, 
as a Bank


By:                                                     
Title:                                          


UNION BANK OF CALIFORNIA, N.A.,
as a Bank

By:                                             
Title: