EXHIBIT 8.1

[Letterhead of Cooley Godward LLP]


September __, 2000



Applied Micro Circuits Corporation
6290 Sequence Drive
San Diego, CA 92121


Ladies and Gentlemen:

This opinion is being delivered to you in connection with the Form S-4
Registration Statement (the "Registration Statement") filed pursuant to the
Agreement and Plan of Merger and Reorganization dated as of August 28, 2000,
(the "Reorganization Agreement") by and among Applied Micro Circuits
Corporation, a Delaware corporation ("Parent"), Mercury Acquisition Corp., a
Delaware corporation and wholly owned subsidiary of Parent ("Merger Sub"), and
MMC Networks, Inc., a Delaware corporation (the "Company").

Except as otherwise provided, capitalized terms used but not defined herein
shall have the meanings set forth in the Reorganization Agreement. All section
references, unless otherwise indicated, are to the Internal Revenue Code of
1986, as amended (the "Code").

We have acted as counsel to Parent in connection with the Merger. As such, and
for the purpose of rendering this opinion, we have examined, and are relying
upon (without any independent investigation or review thereof) the truth and
accuracy, at all relevant times, of the statements, covenants, representations
and warranties contained in the following documents (including all exhibits and
schedules attached thereto):

     (a) the Reorganization Agreement;

     (b) the Registration Statement;

     (c) those certain tax representation letters dated September __, 2000, and
delivered to us by Parent, Merger Sub and the Company (the "Tax Representation
Letters"); and

     (d) such other instruments and documents related to the formation,
organization and operation of Parent, Merger Sub and the Company and to the
consummation of the Merger and the other transactions contemplated by the
Reorganization Agreement as we have deemed necessary or appropriate.

In connection with rendering this opinion, we have assumed (without any
independent investigation or review thereof) that:


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September __, 2000
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     (a) Original documents submitted to us (including signatures thereto) are
authentic, documents submitted to us as copies conform to the original
documents, and that all such documents have been (or will be by the Effective
Time) duly and validly executed and delivered where due execution and delivery
are a prerequisite to the effectiveness thereof;

     (b) All representations, warranties and statements made or agreed to by
Parent, Merger Sub and the Company, their managements, employees, officers,
directors and stockholders in connection with the Merger, including, but not
limited to, those set forth in the Reorganization Agreement (including the
exhibits thereto) and the Tax Representation Letters are true and accurate at
all relevant times;

     (c) All covenants contained in the Reorganization Agreement (including
exhibits thereto) and the Tax Representation Letters are performed without
waiver or breach of any material provision thereof;

     (d) The Merger will be reported by Parent and the Company on their
respective federal income tax returns in a manner consistent with the opinion
set forth below;

     (e) The Merger will be consummated in accordance with the Reorganization
Agreement without any waiver or breach of any material provision thereof, and
the Merger will be effective under applicable state law;

     (f) Any representation or statement made "to the knowledge of" or similarly
qualified is correct without such qualification; and

     (g) The opinion dated September __, 2000, rendered by Wilson Sonsini
Goodrich & Rosati, P.C., to the Company pursuant to the Reorganization Agreement
has been delivered and has not been withdrawn.

Based on our examination of the foregoing items and subject to the limitations,
qualifications, assumptions and caveats set forth herein, we believe that the
discussion entitled "Material U.S. Federal Income Tax Consequences" contained in
the Registration Statement, insofar as it relates to statements of law and legal
conclusions, sets forth the material federal income tax considerations generally
applicable to the Merger.

This opinion does not address the various state, local or foreign tax
consequences that may result from the Merger or the other transactions
contemplated by the Reorganization Agreement. In addition, no opinion is
expressed as to any federal income tax consequence of the Merger or the other
transactions contemplated by the Reorganization Agreement except as specifically
set forth herein, and this opinion may not be relied upon except with respect to
the consequences specifically discussed herein. No opinion is expressed as to
the federal income tax treatment that


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September __, 2000
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may be relevant to a particular investor in light of personal circumstances or
to certain types of investors subject to special treatment under the federal
income tax laws (for example, financial institutions, insurance companies,
foreign individuals and entities, tax-exempt entities, dealers in securities,
persons who are subject to the alternative minimum tax provisions of the Code,
persons who acquired their shares of Company capital stock pursuant to the
exercise of an employee option (or otherwise as compensation), persons whose
shares of Company capital stock are qualified small business stock for purposes
of Section 1202 of the Code, or persons who acquired Company capital stock as
part of an integrated investment, such as a "hedge," "straddle," or other risk
reduction transaction, composed of Company capital stock and one or more other
positions).

No opinion is expressed as to any transaction other than the Merger as described
in the Reorganization Agreement, or as to any transaction whatsoever, including
the Merger, if any of the representations, warranties, statements and
assumptions material to our opinion and upon which we have relied are not
accurate and complete in all material respects at all relevant times.

This opinion only represents our best judgment as to the federal income tax
consequences of the Merger and is not binding on the Internal Revenue Service or
any court of law, tribunal, administrative agency or other governmental body.
The conclusions are based on the Code, existing judicial decisions,
administrative regulations and published rulings. No assurance can be given that
future legislative, judicial or administrative changes or interpretations would
not adversely affect the accuracy of the conclusions stated herein.
Nevertheless, by rendering this opinion, we undertake no responsibility to
advise you of any new developments in the application or interpretation of the
federal income tax laws.

This opinion is being delivered solely in connection with the filing of the
Registration Statement. It is intended for the benefit of Parent and may not be
relied upon or utilized for any other purpose or by any other person and may not
be made available to any other person without our prior written consent.


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September __, 2000
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We consent to the reference to our firm under the caption "Material U.S. Federal
Income Tax Consequences" in the Proxy Statement included in the Registration
Statement and to the reproduction and filing of this opinion as an exhibit to
the Registration Statement.

Sincerely,



SCP:ls