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. 333-45118 on Form S-8 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 3,016,073  shares (the "Shares") of PMC
common stock to be issued under PMC's assumed Quantum Effect Devices,  Inc. 1999
Equity  Incentive  Plan,   Quantum  Effect  Devices,   Inc.,  1999  Non-Employee
Directors'  Stock Option Plan and Quantum  Effect  Devices,  Inc.  1999 Employee
Stock Purchase Plan ("QED Plans").

         It is our opinion that, when shares of PMC are issued and sold pursuant
to the QED Plans, 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