UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                  SCHEDULE 13G


                    UNDER THE SECURITIES EXCHANGE ACT of 1934
                               (AMENDMENT NO. 7 )*

                              Microsemi Corporation
                                (NAME OF ISSUER)

                                  Common Stock
                         (TITLE OF CLASS OF SECURITIES)

                                    595137100
                                 (CUSIP NUMBER)

                                December 31, 1998
             (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT)

 Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

     [ X  ]  Rule 13d-1(b)

     [    ]  Rule 13d-1(c)

     [    ]  Rule 13d-1(d)

*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for any  subsequent  amendment  containing  information  which  would  alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the Notes)





CUSIP NO. 595137100       13G

1     NAME OF REPORTING PERSON
      S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
          Rockefeller & Co., Inc.
          I.R.S. Identification No.: 13-3006584

2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
          Not applicable           (a)       |_|
                                   (b)       |_|

3    SEC USE ONLY

4    CITIZENSHIP OR PLACE OF ORGANIZATION
          New York

                              5    SOLE VOTING POWER
NUMBER OF                           Not applicable.

SHARES                        6    SHARED VOTING POWER
                                    Not applicable.
BENEFICIALLY
                              7    SOLE DISPOSITIVE POWER
OWNED BY                            Not applicable

EACH REPORTING                8    SHARED DISPOSITIVE POWER
                                    Not applicable.
PERSON WITH

9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
      Not applicable.

10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
CERTAIN SHARES*
      Not applicable.

11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
      Not applicable.

12   TYPE OF REPORTING PERSON*
      IA
               *SEE INSTRUCTION BEFORE FILLING OUT!


Item 1(a).  Name of Issuer:

         Microsemi Corporation

Item 1(b).  Address of Issuer's Principal Executive Offices:

          2830 South Fairview Street
          Santa Ana, California  92704

Item 2(a).  Name of Person Filing:

            Rockefeller & Co., Inc.

Item 2(b).  Address of Principal Business Office:

            30 Rockefeller Plaza, New York, New York 10112

Item 2(c).  Citizenship:

            New York

Item 2(d).  Title of Class of Securities:

            Common Stock

Item 2(e).  CUSIP Number:

            595137100

Item 3.     If this  statement  is filed  pursuant  to Rules  13d-  1(b),  or
            13d-2(b), check whether the person filing is a:

(a)         Broker or Dealer registered under Section 15 of
            the Act,

(b)         Bank as defined in Section 3(a)(6) of the Act,

(c)         Insurance Company as defined in Section 3(a)(19) of
            the Act,

(d)         Investment  Company  registered  under  Section 8 of the  Investment
            Company Act,

(e) X       Investment  Adviser registered under Section 203 of the Investment
            Advisers Act of 1940,



(f)         Employee  Benefit  Plan,  Pension  Fund  which  is  subject  to  the
            provisions of the Employee Retirement Income Security Act of 1974 or
            Endowment Fund; see 13d-(b)(1)(ii)(F),

(g)         Parent Holding Company, in accordance with
            Rule 13d-1(b)(ii)(G),

(h)         Group, in accordance with Rule 13d-1(b)(1)(ii)(H).


Item 4.     Ownership

         Not applicable.


Item 5.   Ownership of Five Percent or Less of a Class.

         If this statement is being filed to report the fact that as of the date
hereof the reporting  person has ceased to be the beneficial  owner of more than
five percent of the class of securities, check the following [X].

Item 6.   Ownership of More than Five Percent on Behalf of
          Another Person.

         Not Applicable.

 Item 7.   Identification and Classification of the Subsidiary
         Which Acquired the Security Being Reported on By the Parent
         Holding Company.

         Not Applicable.

Item 8.   Identification and Classification of Members of the Group.

          Not Applicable.

Item 9.   Notice of Dissolution of Group.

          Not Applicable.




Item 10.  Certification.

Inasmuch as the reporting  person is no longer the beneficial owner of more than
5 percent of the number of shares  outstanding  of the issuer of the  securities
referenced  herein,  the reporting  person has no further  reporting  obligation
under Section 13(d) of the Securities Act with respect to such issuer.


          SIGNATURE

          After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information  set forth in this statement is true,  complete and
correct.

February 12, 1999
(Date)



(Signature) /s/ David A. Strawbridge

David A. Strawbridge, Vice President
(Name/Title)