Exhibit 10.4.5

                               KOMAG, INCORPORATED

                       1997 SUPPLEMENTAL STOCK OPTION PLAN
                       -----------------------------------

                             (Amended June 12, 1998)

                                   ARTICLE ONE

                               GENERAL PROVISIONS
                               ------------------

       I.         PURPOSES OF THE PLAN

                  This 1997 Non-Executive Officer Stock Option Plan (the "Plan")
is  intended  to  promote  the  interests  of Komag,  Incorporated,  a  Delaware
corporation  (the  "Corporation"),   by  providing  a  method  whereby  eligible
individuals  may be offered  incentives and rewards which will encourage them to
acquire  a  proprietary   interest,  or  otherwise  increase  their  proprietary
interest,  in the Corporation and continue to render services to the Corporation
(or its parent or subsidiary corporations).

      II.         ADMINISTRATION OF THE PLAN

                  A. The Plan shall be  administered  by one or more  committees
comprised of Board members (the  "Committee")  or the Board may retain the power
to administer the Plan.  The members of the Committee  shall each serve for such
period of time as the Board may determine and shall be subject to removal by the
Board at any time.

                  B.  The  Committee  (or the  Board  if no  Committee  has been
designated) shall serve as the Plan  Administrator and shall have full power and
authority  (subject to the express  provisions  of the Plan) to  establish  such
rules and regulations as it may deem  appropriate for the proper  administration
of such  program  and to make  such  determinations  under the  program  and any
outstanding option as it may deem necessary or advisable.  Decisions of the Plan
Administrator  shall be final and binding on all parties with an interest in the
Plan or any options or shares issued hereunder.

     III.         ELIGIBILITY FOR OPTION GRANTS

                  A.  The persons eligible to participate in the Plan shall be

                          -         employees (excluding officers and directors)
         of the Corporation (or its parent or subsidiary corporations), or

                          -         independent  contractors and consultants who
         provide  valuable  services  to  the  Corporation  (or  its  parent  or
         subsidiary corporations).

                  B. The Plan Administrator  shall have full authority to select
the eligible  individuals  who are to receive  option grants under the Plan, the
number of shares to be  covered  by each  granted  option,  the time or times at
which such option is to become  exercisable  and the maximum  term for which the
option is to be outstanding.

                  C. For purposes of the Plan, the following provisions shall be
applicable  in  determining  the  parent  and  subsidiary  corporations  of  the
Corporation:

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                           Any  corporation  (other than the  Corporation) in an
         unbroken chain of  corporations  ending with the  Corporation  shall be
         considered to be a parent corporation of the Corporation, provided each
         such  corporation  in the unbroken  chain (other than the  Corporation)
         owns, at the time of the determination,  stock possessing fifty percent
         (50%) or more of the total  combined  voting  power of all  classes  of
         stock in one of the other corporations in such chain.

                           Each  corporation  (other than the Corporation) in an
         unbroken chain of corporations  beginning with the Corporation shall be
         considered  to be a subsidiary of the  Corporation,  provided each such
         corporation  (other than the last  corporation)  in the unbroken  chain
         owns, at the time of the determination,  stock possessing fifty percent
         (50%) or more of the total  combined  voting  power of all  classes  of
         stock in one of the other corporations in such chain.

      IV.         STOCK SUBJECT TO THE PLAN

                  A. The stock  issuable  under the Plan  shall be shares of the
Corporation's  authorized but unissued or reacquired Common Stock. The aggregate
number of shares  which may be issued over the term of the Plan shall not exceed
Six Million One Hundred Thousand  (6,100,000) shares (subject to adjustment from
time to time in accordance with paragraph IV.C of this Article One).

                  B.  Should an option be  terminated  for any  reason  prior to
exercise  in whole or in part,  the shares  subject to the portion of the option
not so exercised  shall be available  for  subsequent  option  grants under this
Plan.  In  addition,  unvested  shares  issued  under the Plan and  subsequently
repurchased by the  Corporation  at the original  exercise price paid per share,
pursuant to the  Corporation's  repurchase  rights under the Plan shall be added
back to the number of shares of Common Stock  reserved  for  issuance  under the
Plan and shall  accordingly  be  available  for  reissuance  through one or more
subsequent option grants under the Plan.

                  C.  In the  event  any  change  is made  to the  Common  Stock
issuable  under the Plan  (whether  by reason of (i)  merger,  consolidation  or
reorganization   or  (ii)   recapitalization,   stock  dividend,   stock  split,
combination of shares,  exchange of shares or other similar change affecting the
outstanding  Common  Stock  as a class  without  the  Corporation's  receipt  of
consideration),  then  unless  such  change  results in the  termination  of all
outstanding options pursuant to the provisions of paragraph II of Article Two of
the Plan,  appropriate  adjustments  shall be made to (i) the  aggregate  number
and/or class of shares issuable under the Plan, and (ii) the number and/or class
of shares and price per share in effect under each outstanding  option under the
Plan.  The purpose of such  adjustments to the  outstanding  options shall be to
preclude the enlargement or dilution of rights and benefits under such options.

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<PAGE>

                                   ARTICLE TWO

                              OPTION GRANT PROGRAM
                              --------------------


       I.         TERMS AND CONDITIONS OF OPTIONS

                  Options  granted   pursuant  to  this  Article  Two  shall  be
authorized  by  action  of the Plan  Administrator  and  shall be  Non-Statutory
Options.  The granted  options shall be evidenced by instruments in such form as
the Plan Administrator shall from time to time approve; provided,  however, that
each such instrument  shall comply with and incorporate the terms and conditions
specified below.

                  A.       Option Price.

                           1.       The option price per share shall be fixed by
the Plan Administrator.  In no event, however,  shall the option price per share
be less than one hundred  percent  (100%) of the fair market  value per share of
Common Stock on the date of the option grant.

                           2.       The option  price shall  become  immediately
due upon exercise of the option and shall be payable as follows:

                                 (i)        full  payment in cash or check drawn
         to the Corporation's order;

                                (ii)        full  payment  in  shares  of Common
         Stock held by the optionee for the requisite  period necessary to avoid
         a charge to the Corporation's earnings for financial reporting purposes
         and valued at fair market value on the  Exercise  Date (as such term is
         defined below) equal to the option price; or

                               (iii)        full payment  through a  combination
         of shares of Common Stock held by the optionee for the requisite period
         necessary to avoid a charge to the Corporation's earnings for financial
         reporting purposes and valued at fair market value on the Exercise Date
         and cash or check, equal in the aggregate to the option price.

                                (iv)        to  the   extent   the   option   is
         exercised for vested shares,  the option price may also be paid through
         a  broker-dealer  sale and remittance  procedure  pursuant to which the
         optionee   shall   provide   irrevocable    instructions   to   (I)   a
         Corporation-designated  brokerage  firm to effect the immediate sale of
         the  purchased  shares  and remit to the  Corporation,  out of the sale
         proceeds  available  on the  settlement  date,  an amount  equal to the
         aggregate  option  price  payable  for the  purchased  shares  plus all
         applicable Federal and State income and employment taxes required to be
         withheld by the  Corporation  by reason of such  purchase  and (II) the
         Corporation  to  deliver  the  certificates  for the  purchased  shares
         directly to such brokerage firm.

                           For  purposes of this  subparagraph  2, the  Exercise
Date  shall  be the  date on which  notice  of the  exercise  of the  option  is
delivered  to the  Corporation.  Except to the  extent 

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the sale and remittance procedure is utilized in connection with the exercise of
the option,  payment of the option price for the purchased shares must accompany
such notice.

                           3.       The fair  market  value of a share of Common
Stock on any relevant  date under  subparagraph  1 or 2 above (and for all other
valuation  purposes  under the Plan) shall be determined in accordance  with the
following provisions:

                                 (i)        If the  Common  Stock is at the time
         traded on the Nasdaq National Market,  then the fair market value shall
         be the closing selling price per share of Common Stock on the day prior
         to the date in  question,  as such price is  reported  by the  National
         Association of Securities  Dealers on the Nasdaq National Market or any
         successor  system.  If there is no closing selling price for the Common
         Stock on the day prior to the date in  question,  then the fair  market
         value shall be the closing selling price on the last preceding date for
         which such quotation exists.

                                (ii)        If the  Common  Stock is at the time
         listed on either  the New York Stock  Exchange  or the  American  Stock
         Exchange, then the fair market value shall be the closing selling price
         per share of Common  Stock on the day prior to the date in  question on
         such exchange, as such price is officially quoted in the composite tape
         of transactions on that exchange.  If there is no closing selling price
         for the Common Stock on the day prior to the date in question, then the
         fair  market  value  shall  be the  closing  selling  price on the last
         preceding date for which such quotation exists.

                  B.       Term and Exercise of Options.

                           Each option  granted  under this Article Two shall be
exercisable  at such time or times,  during such period,  and for such number of
shares as shall be  determined  by the Plan  Administrator  and set forth in the
instrument  evidencing such option;  provided,  however,  that no option granted
under this  Article  Two shall  have a maximum  term in excess of ten (10) years
from the grant date.

                  C.       Limited Transferability of Options.

                           During the lifetime of the optionee, the option shall
be exercisable  only by the optionee and shall not be assignable or transferable
by  the  optionee  otherwise  than  by  will  or by  the  laws  of  descent  and
distribution following the optionee's death. However, the Plan Administrator may
grant one or more options under this Article Two which may, in  connection  with
the  optionee's  estate  plan,  be  assigned  in  whole  or in part  during  the
optionee's lifetime to one or more members of the optionee's immediate family or
to a trust  established  exclusively  for one or more such family  members.  The
assigned  portion may only be  exercised  by the person or persons who acquire a
proprietary  interest  in the  option  pursuant  to the  assignment.  The  terms
applicable to the assigned  portion shall be the same as those in effect for the
option  immediately  prior to such  assignment  and  shall be set  forth in such
documents issued to the assignee as the Plan Administrator may deem appropriate.

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<PAGE>

                  D.       Termination of Service.

                           1.       Should  an  optionee   cease  to  remain  in
Service for any reason (including death,  permanent  disability or retirement at
or after age 65) while the holder of one or more outstanding  options granted to
such optionee  under the Plan,  then such option or options shall not (except to
the  extent  otherwise   provided   pursuant  to  paragraph  VII  below)  remain
exercisable for more than a twelve  (12)-month period (or such shorter period as
is determined by the Plan  Administrator  and set forth in the option agreement)
following  the date of cessation of Service;  provided,  however,  that under no
circumstances   shall  any  such  option  be  exercisable  after  the  specified
expiration  date of the option  term.  Except to the extent  otherwise  provided
pursuant to subparagraph I.D.4 below, each such option shall, during such twelve
(12)-month or shorter  period,  be exercisable  for any or all vested shares for
which that option is exercisable on the date of such cessation of Service.  Upon
the expiration of such twelve  (12)-month or shorter period or (if earlier) upon
the  expiration of the option term,  the option shall  terminate and cease to be
exercisable  for any such  vested  shares  for  which  the  option  has not been
exercised.  However, the option shall, immediately upon the optionee's cessation
of Service,  terminate  and cease to be  outstanding  with respect to any option
shares in which the  optionee is not  otherwise at that time vested or for which
the option is not otherwise at that time exercisable.

                           2.       Should the optionee die while in Service, or
cease to remain in Service  and  thereafter  die while the holder of one or more
outstanding  options  under the Plan,  each such option may be  exercised by the
personal  representative of the optionee's estate or by the person or persons to
whom the option is transferred  pursuant to the optionee's will or in accordance
with the laws of descent and  distribution  but, except to the extent  otherwise
provided pursuant to subparagraph  I.D.4 below, only to the extent of the number
of vested shares (if any) for which the option is exercisable on the date of the
optionee's death. Such exercise must be effected prior to the earlier of (i) the
first  anniversary  of the date of the  optionee's  death or (ii) the  specified
expiration  date of the option term.  Upon the  occurrence of the earlier event,
the option shall terminate and cease to be exercisable.

                           3.       If (i) the optionee's  Service is terminated
for  cause  (including,  but not  limited  to,  any act of  dishonesty,  willful
misconduct,  fraud or  embezzlement  or any  unauthorized  disclosure  or use of
confidential  information  or  trade  secrets)  or (ii)  the  optionee  makes or
attempts to make any unauthorized use or disclosure of confidential  information
or trade secrets of the  Corporation  or its parent or subsidiary  corporations,
then in any such event all  outstanding  options  granted the optionee under the
Plan shall terminate and cease to be exercisable immediately upon such cessation
of  Service  or  (if  earlier)  upon  such  unauthorized  use or  disclosure  of
confidential or secret information or attempt thereat.

                           4.       The Plan  Administrator  shall have complete
discretion,  exercisable either at the time the option is granted or at the time
the optionee  dies,  retires at or after age 65, or ceases to remain in Service,
to  establish as a provision  applicable  to the exercise of one or more options
granted  under  the Plan  that  during  the  limited  period  of  exercisability
following death,  retirement at or after age 65, or cessation of Employee status
as provided in  subparagraph  I.D.1 or I.D.2 above,  the option may be exercised
not only with respect to the number of vested shares for which it is exercisable
at the time of the optionee's cessation of Service, but also with respect to one
or more  subsequent  installments  in which the  optionee  would have  otherwise
vested had such cessation of Service not occurred.

                           5.       For purposes of the foregoing  provisions of
this paragraph I.D (and all other provisions of the Plan),

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<PAGE>

                           -        The  optionee  shall be  deemed to remain in
         the Service of the Corporation  for so long as such individual  renders
         services  on a  periodic  basis to the  Corporation  (or any  parent or
         subsidiary  corporation) in the capacity of an Employee, a non-employee
         member of the Board or an independent consultant or advisor.

                           -        The optionee  shall be  considered  to be an
         Employee  for so long as such  individual  remains in the employ of the
         Corporation  or one or more of its parent or  subsidiary  corporations,
         subject to the control and direction of the employer not only as to the
         work  to be  performed  but  also  as  to  the  manner  and  method  of
         performance.

                  D.       Stockholder Rights.

                           An option  holder  shall have none of the rights of a
stockholder  with  respect  to any  shares  covered  by the  option  until  such
individual  shall have  exercised  the  option,  paid the option  price and been
issued a stock certificate for the purchased shares. No adjustment shall be made
for  dividends  or  distributions  (whether  paid in cash,  securities  or other
property)  for which the record date is prior to the date the stock  certificate
is issued.

                  E.       Repurchase Rights.

                           The shares of Common Stock acquired upon the exercise
of options  granted  under this Article Two may be subject to  repurchase by the
Corporation in accordance with the following provisions:

                           The Plan  Administrator  shall have the discretion to
authorize  the  issuance of unvested  shares of Common  Stock under this Article
Two. Should the Optionee cease Service while holding such unvested  shares,  the
Corporation  shall  have the right to  repurchase  any or all of those  unvested
shares at the option price paid per share.  The terms and conditions  upon which
such repurchase  right shall be exercisable  (including the period and procedure
for exercise and the  appropriate  vesting  schedule for the  purchased  shares)
shall be established by the Plan  Administrator  and set forth in the instrument
evidencing such repurchase right.

                           All  of  the  Corporation's   outstanding  repurchase
rights shall automatically  terminate, and all shares subject to such terminated
rights shall  immediately  vest in full,  upon the  occurrence  of any Corporate
Transaction  under paragraph II of this Article Two,  except to the extent:  (i)
any such  repurchase  right is to be assigned to the successor  corporation  (or
parent  thereof)  in  connection  with the  Corporate  Transaction  or (ii) such
termination is precluded by other limitations  imposed by the Plan Administrator
at the time the repurchase right is issued.

                           The Plan  Administrator  shall have the discretionary
authority,  exercisable  either  before or after  the  optionee's  cessation  of
Service, to cancel the Corporation's  outstanding repurchase rights with respect
to one or more  shares  purchased  or  purchasable  by the  optionee  under this
Article Two and thereby accelerate the vesting of such shares in connection with
the optionee's cessation of Service.

      II.         CORPORATE TRANSACTIONS


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<PAGE>

                  A.       In   the    event    of   any   of   the    following
stockholder-approved transactions (a "Corporate Transaction"):

                                (i)         a merger or acquisition in which the
         Corporation is not the surviving  entity,  except for a transaction the
         principal  purpose of which is to change the State of the Corporation's
         incorporation,

                                (ii)        the   sale,   transfer    or   other
         disposition  of  all  or  substantially   all  of  the  assets  of  the
         Corporation, or

                               (iii)        any  reverse  merger  in  which  the
         Corporation is the surviving entity,

                           then each option  outstanding  under this Article Two
shall automatically become exercisable,  during the five (5) business day period
immediately prior to the specified effective date for the Corporate Transaction,
with respect to the full number of shares of Common Stock purchasable under such
option  and may be  exercised  for all or any  portion  of such  shares as fully
vested shares of Common Stock. An outstanding option under the Plan shall not be
so accelerated,  however, if and to the extent (i) such option is, in connection
with  the  Corporate  Transaction,   either  to  be  assumed  by  the  successor
corporation  or  parent  thereof  or be  replaced  with a  comparable  option to
purchase  shares of the capital  stock of the  successor  corporation  or parent
thereof or (ii) the acceleration of such option is subject to other  limitations
imposed by the Plan Administrator at the time of grant.

                  B.       Immediately   following  the   consummation   of  the
Corporate  Transaction,  all  outstanding  options under the Plan shall,  to the
extent not previously  exercised or assumed by the successor  corporation or its
parent company, terminate and cease to be exercisable.

                  C.       Each outstanding  option under this Article Two which
is assumed in  connection  with the  Corporate  Transaction  or is  otherwise to
continue  in effect  shall be  appropriately  adjusted,  immediately  after such
Corporate  Transaction,  to  apply  and  pertain  to the  number  and  class  of
securities  which would have been issuable,  in  consummation  of such Corporate
Transaction, to an actual holder of the same number of shares of Common Stock as
are  subject to such option  immediately  prior to such  Corporate  Transaction.
Appropriate  adjustments  shall also be made to the  option  price  payable  per
share,  provided the aggregate  option price payable for such  securities  shall
remain the same. In addition,  the class and number of securities  available for
issuance under the Plan following the consummation of the Corporate  Transaction
shall be appropriately adjusted.

                  D.       Option  grants under this Article Two shall in no way
affect  the  right of the  Corporation  to  adjust,  reclassify,  reorganize  or
otherwise  change its capital or business  structure  or to merge,  consolidate,
dissolve,  liquidate  or sell or  transfer  all or any part of its  business  or
assets.

     III.         CANCELLATION AND REGRANT

                  The Plan Administrator  shall have the authority to effect, at
any time and from time to time, with consent of the affected option holders, the
cancellation  of any or all  outstanding  options under the Plan and to grant in
substitution  therefor new options  covering  the same or  different  numbers of
shares of Common  Stock but  having  an  exercise  price per share  

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equal to one hundred percent (100%) of the fair market value of the Common Stock
on the new grant date.

      IV.         EXTENSION OF EXERCISE PERIOD

                  The Plan  Administrator  shall have full power and  authority,
exercisable from time to time in its sole discretion,  to extend,  either at the
time the option is granted or at any time while such option remains outstanding,
the period of time for which the option is to remain  exercisable  following the
optionee's  cessation of Service or death from the twelve  (12)-month or shorter
period set forth in the option  agreement to such greater  period of time as the
Plan Administrator shall deem appropriate;  provided,  however, that in no event
shall such option be  exercisable  after the  specified  expiration  date of the
option term.


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<PAGE>

                                  ARTICLE THREE

                                  MISCELLANEOUS
                                  -------------

       I.         AMENDMENT OF THE PLAN

                  The  Board  shall  have  complete  and  exclusive   power  and
authority  to  amend  or  modify  the  Plan in any or all  respects  whatsoever.
However,  no such amendment or  modification  shall,  without the consent of the
holders,  adversely affect rights and obligations with respect to options at the
time outstanding under the Plan.

      II.         EFFECTIVE DATE AND TERM OF PLAN

                  A. The Plan shall  become  effective  upon its adoption by the
Board.  Unless sooner terminated in accordance with paragraph II of Article Two,
the Plan shall  terminate upon the earlier of (i) September 26, 2007 or (ii) the
date on which all shares  available for issuance  under the Plan shall have been
issued or cancelled  pursuant to the  exercise or  surrender of options  granted
hereunder. If the date of termination is determined under clause (i) above, then
options outstanding on such date shall not be affected by the termination of the
Plan and  shall  continue  to have  force  and  effect  in  accordance  with the
provisions of the instruments evidencing such options.

                  B. On January 30, 1998, the Board approved an amendment to the
Plan to increase the number of shares of Common Stock reserved for issuance over
the term of the Plan by an additional 1,000,000 shares.

                  C. On June 12,  1998,  the Board  approved an amendment to the
Plan to increase the number of shares of Common Stock reserved for issuance over
the term of the Plan by an additional 1,500,000 shares.


     III.         USE OF PROCEEDS

                  Any cash proceeds received by the Corporation from the sale of
shares  pursuant  to options  granted  under the Plan shall be used for  general
corporate purposes.

      IV.         TAX WITHHOLDING

                  The  Corporation's  obligation to deliver  shares or cash upon
the exercise or surrender of any option  granted under the Plan shall be subject
to the  satisfaction  of all  applicable  federal,  state and local  income  and
employment tax withholding requirements.

       V.         NO EMPLOYMENT/SERVICE RIGHTS

                  Neither  the  action of the  Corporation  in  establishing  or
restating the Plan,  nor any action taken by the Plan  Administrator  hereunder,
nor any  provision  of the  restated  Plan shall be construed so as to grant any
individual the right to remain in the employ or service of the  Corporation  (or
any parent or subsidiary  corporation) for any period of specific duration,  and
the Corporation (or any parent or subsidiary  corporation retaining the services
of such individual) may terminate such individual's employment or service at any
time and for any reason, with or without cause.

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<PAGE>

      VI.         REGULATORY APPROVALS

                  A. The  implementation of the Plan, the granting of any option
hereunder,  and the issuance of stock upon the exercise or surrender of any such
option shall be subject to the  Corporation's  procurement  of all approvals and
permits required by regulatory  authorities  having  jurisdiction over the Plan,
the options granted under it and the stock issued pursuant to it.

                  B. No shares of Common  Stock or other  assets shall be issued
or  delivered  under the Plan unless and until there shall have been  compliance
with all applicable requirements of Federal and state securities laws, including
the filing and  effectiveness  of the Form S-8  registration  statement  for the
shares of Common  Stock  issuable  under the Plan,  and all  applicable  listing
requirements  of  any  stock  exchange  (or  the  Nasdaq  National  Market,   if
applicable) on which Common Stock is then listed for trading.


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