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                                                                     Exhibit 8.1
                       [WILSON SONSINI GOODRICH & ROSATI,
                      PROFESSIONAL CORPORATION LETTERHEAD]

                                October 10, 2000

Sun Microsystems, Inc.
901 San Antonio Road
Palo Alto, California 94303

         RE: MERGER AMONG SUN MICROSYSTEMS, INC., A DELAWARE CORPORATION
             ("SUN"), AZURE ACQUISITION CORPORATION, A DELAWARE CORPORATION
             ("AZURE"), AND COBALT NETWORKS, INC., A DELAWARE CORPORATION
             ("COBALT")

Ladies and Gentlemen:

     We have acted as counsel to Sun in connection with the proposed merger (the
"Merger") of Sun's wholly-owned transitory merger subsidiary, Azure, with and
into Cobalt pursuant to an Agreement and Plan of Merger and Reorganization dated
as of September 18, 2000 (the "Merger Agreement"). The Merger and certain
proposed transactions incident thereto are described in the Registration
Statement on Form S-4 (the "Registration Statement") of Sun which includes the
Proxy Statement/Prospectus of Sun and Cobalt (the "Proxy Statement/Prospectus").
This opinion is being rendered pursuant to the requirements of Item 21(a) of
Form S-4 under the Securities Act of 1933, as amended. Unless otherwise
indicated, any capitalized terms used herein and not otherwise defined have the
meaning ascribed to them in the Merger Agreement.

     In connection with this opinion, we have examined and are familiar with the
Merger Agreement, the Registration Statement, and such other presently existing
documents, records and matters of law as we have deemed necessary or appropriate
for purposes of our opinion. In addition, we have assumed (i) that the Merger
will be consummated in the manner contemplated by the Proxy Statement/Prospectus
and in accordance with the provisions of the Merger Agreement, (ii) the truth
and accuracy of the representations and warranties made by Sun, Cobalt and Azure
in the Merger Agreement, and (iii) the truth and accuracy of the certificates of
representations to be provided to us by Sun, Cobalt, and Merger Sub.

     Because this opinion is being delivered prior to the Effective Time of the
Merger, it must be considered prospective and dependent on future events. There
can be no assurance that changes in the law will not take place which could
affect the United States Federal income tax consequences of the Merger or that
contrary positions may not be taken by the Internal Revenue Service.

     Based upon and subject to the foregoing, in our opinion, the discussion
contained in the Registration Statement under the caption "Material U.S. Federal
Income Tax Consequences,"


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Sun Microsystems, Inc.
October 10, 2000
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subject to the limitations and qualifications described therein, sets forth the
material United States Federal income tax consequences generally applicable to
the Merger.

     This opinion is furnished to you solely for use in connection with the
Registration Statement. We hereby consent to the filing of this opinion as an
Exhibit to the Registration Statement. We also consent to the reference to our
firm name wherever appearing in the Registration Statement with respect to the
discussion of the material federal income tax consequences of the Merger,
including the Proxy Statement/Prospectus constituting a part thereof, and any
amendment thereto. In giving this consent, we do not thereby admit that we are
in the category of persons whose consent is required under Section 7 of the
Securities Act of 1933, as amended, or the rules and regulations of the
Securities and Exchange Commission thereunder, nor do we thereby admit that we
are experts with respect to any part of such Registration Statement within the
meaning of the term "experts" as used in the Securities Act of 1933, as amended,
or the rules and regulations of the Securities and Exchange Commission
thereunder.

                                           Very truly yours,

                                           WILSON SONSINI GOODRICH & ROSATI
                                           Professional Corporation

                                           /s/ Wilson Sonsini Goodrich & Rosati



Palo Alto, California