WILSON SONSINI GOODRICH & ROSATI
                            PROFESSIONAL CORPORATION


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



                                       August 26, 1997


PMC-Sierra, Inc.
105-8555 Baxter Place
Burnaby, British Columbia
Canada  V5A 4V7

         Re:  Registration Statement on Form S-3 (File No. 33-90392)
              ------------------------------------------------------

Gentlemen & Ladies:

         We have examined the Post-effective Amendment No. 1 to the Registration
Statement  on Form  S-3 to be filed by you  with  the  Securities  and  Exchange
Commission  (the  "Registration  Statement") in connection with your adoption of
the registration under the Securities Act of 1933, as amended, of shares of your
Common Stock (the "Shares") registered under the Registration  Statement on Form
S-3 (No. 33-90392). As your counsel in connection with this transaction, we have
examined the proceedings taken and are familiar with the proceedings proposed to
be taken by you in  connection  with the  issuance and sale of the Shares in the
manner set forth in the Registration Statement.

         It is our opinion that, when issued and sold in the manner set forth in
the  Registration  Statement,  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 and any amendments thereto.

                                       Very truly yours,

                                       /s/ WILSON SONSINI GOODRICH & ROSATI

                                       WILSON SONSINI GOODRICH & ROSATI
                                       Professional Corporation