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                                                                    EXHIBIT 10.4


                                PROMISSORY NOTE

$12,273,650.11                                               September 2, 2001


      1.    Principal and Interest. MMC Technology, Inc. (the "Company"), a
California corporation, for value received, hereby promises to pay to the order
of Hynix Semiconductor America Inc. ("Payee") in lawful money of the United
States at the principal office of the Company, the principal sum of Twelve
Million Two Hundred Seventy Three Thousand Six Hundred Fifty Dollars and Eleven
Cents ($12,273,650.11), payable as follows:

      (a)   a principal amount of Five Million Dollars ($5,000,000.00) at the
closing of the transactions contemplated in the Agreement and Plan of
Reorganization dated as of August 17, 2001 to which the Company and the Payee
are each a party (the "Closing"); and

      (b)   following payment of the amount in Section 1(a), the outstanding
principal balance hereunder in the amount of Seven Million Two Hundred Seventy
Three Thousand Six Hundred Fifty Dollars and Eleven Cents ($7,273,650.11), on
or before March 31, 2002; provided, however, that in the event that the
principal amount set forth in this Section 1(b) is not paid in full on or before
March 31, 2002, such unpaid principal amount shall thereafter accrue interest at
a rate per annum equal to nine percent (9%) and all accrued and unpaid interest
shall be due and payable on demand by Payee. Except as expressly set forth in
this Section 1(b), this Promissory Note shall not bear any interest.

      2.    Attorneys' Fees. If the indebtedness represented by this Note or any
part thereof is the subject of an action in bankruptcy, receivership or other
judicial proceedings or if this Note is placed in the hands of attorneys for
collection after default, Company agrees to pay, in addition to the due and
unpaid principal and interest payable hereunder, reasonable and documented
attorneys' fees and reasonable and documented costs incurred by Payee.

      3.    Prepayment. The indebtedness represented by this Note may be
pre-paid by the Company at any time without penalty or any other charge or
assessment.

      4.    Acceleration. The indebtedness represented by this Note shall become
immediately due and payable if (i) the Company commences any proceeding in
bankruptcy or for dissolution, liquidation, winding-up, or other relief under
state or federal bankruptcy laws; or (ii) such proceedings are commenced against
the Company, or a receiver or trustee is appointed for the Company or a
substantial part of its property, and such proceeding or appointment is not
dismissed or discharged within 60 days after its commencement.

      5.    Waivers. Company hereby waives presentment, demand for performance,
notice of non-performance, protest, notice of protest and notice of dishonor. No
delay on the part of Payee in exercising any right hereunder shall operate as a
waiver of such right or any other right. This Note is being delivered in and
shall be construed in accordance with the laws of the State of California,
without regard to the conflicts of laws provisions hereof.


                                          MMC Technology, Inc.


                                          By:  /s/ TAJ GUILAMANI
                                             ----------------------------
                                          Its:  Taj Guilamani
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                                                  VP Fin