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                                                                    EXHIBIT 10.1

                     AMENDMENT NO. 1 TO OPTION AGREEMENT III


        This amendment ("Amendment") is effective as of July 2, 1998 (the
"Effective Date") and amends that certain Option Agreement III ("Agreement")
dated April 21, 1997, by and between Adaptec Mfg (S) Pte. Ltd. ("Adaptec") and
Taiwan Semiconductor Manufacturing Co., Ltd. ("TSMC").

        I. Under the terms of the Agreement, the second and final installment
of the Option Fee, in the amount of US$17.64 Million (the "Second Installment"),
is due and payable on June 30, 1998. The parties hereby agree that Adaptec may
defer payment of the Second Installment until such time as Adaptec requires the
Option III Capacity, subject to the following:

                  (a) Adaptec will give TSMC at least one hundred eighty (180)
         days prior written notice of its intent to pay the Second Installment;

                  (b) Until payment of the Second Installment is received by
         TSMC, the Option III Capacity will not be included in the "TSMC
         Committed Capacity" or in the "Customer Committed Capacity" as those
         terms are defined in the Agreement; and

                  (c) The term of the Agreement will be extended by a period
         equal to the time between June 30, 1998 and the date payment of the
         Second Installment is received by TSMC, and the parties' respective
         obligations to purchase and sell the Wafer Equivalents included in the
         Option III Capacity will also be deferred for a like period.

                  (d) The promissory note for the Second Installment issued by
         Adaptec to the order of TSMC dated April 21, 1997 and specifying a due
         date of June 30, 1998 (the "Promissory Note"), is hereby amended by
         deleting the due date specified therein and replacing it with the date
         specified by Adaptec for payment of the Second Installment pursuant to
         paragraph I (a) of this Amendment. TSMC agrees that it will attach a
         fully-executed copy of this Amendment to the original of the Promissory
         Note, and will notify any holder in due course of the Promissory Note
         of the terms of this Amendment.

         II. Except as expressly amended by this Amendment, the Agreement and
the Promissory Note shall continue in full force and effect in accordance with
their terms. In the event of any conflict between the terms of this Amendment
and the terms of the Agreement or of the Promissory Note, this Amendment shall
control.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed
by their duly authorized representatives.

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


By:     [SIG]                        By:     [SIG]

Title:  Vice President               Title:  Vice President
        and Director

Date:   7/2/98                       Date:   7/7/98



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