WILSON SONSINI GOODRICH & ROSATI
                            PROFESSIONAL CORPORATION


                               650 PAGE MILL ROAD
                        PALO ALTO, CALIFORNIA 94304-1050
                  TELEPHONE 650-493-9300 FACSIMILE 650-493-6811


                                October 31, 2000
PMC-Sierra, Inc.
900 East Hamilton Avenue, Suite 250
Campbell, California 95008

       Re:  Post Effective Amendment No. 1 to Registration Statement on Form S-8

Ladies and Gentlemen:

         We  have  examined  Post  Effective  Amendment  No.  1 to  Registration
Statement  No.  333-44212  to be  filed by  PMC-Sierra,  Inc.  ("PMC")  with the
Securities   and  Exchange   Commission  on  or  about  October  31,  2000  (the
"Registration   Statement")  in  connection  with  the  registration  under  the
Securities  Act of 1933,  as amended,  of 40,701  shares (the  "Shares")  of PMC
common stock to be issued under Datum  Telegraphic Inc.  ("Datum") stock options
assumed by PMC pursuant to the Acquisition Agreement dated July 21, 2000 between
PMC,  600444  B.C.  Ltd.,  Datum,  and State  Street  Bank and Trust  Company of
California,  N.A. (the "Acquisition Agreement").  As PMC's counsel in connection
with this  transaction,  we have examined the proceedings taken and are familiar
with the proceedings proposed to be taken by PMC in connection with the issuance
and sale of the Shares pursuant to the Datum stock options.

         It is our opinion that, when shares of PMC are issued and sold pursuant
to the Datum option  agreements,  the Shares will be legally and validly issued,
fully paid and non-assessable.

         We consent to the use of this opinion as an exhibit to the Registration
Statement,  and further consent to the use of our name wherever appearing in the
Registration Statement.

                                           Very truly yours,

                                           /s/ WILSON SONSINI GOODRICH & ROSATI

                                           WILSON SONSINI GOODRICH & ROSATI
                                           Professional Corporation