1
                                                                     EXHIBIT 8.2


                         [COOLEY GODWARD LLP LETTERHEAD]


June ___, 2000


HMT Technology Corp.
1055 Page Avenue
Fremont, CA  94538


Ladies and Gentlemen:

This opinion is being delivered to you in connection with the filing of a
registration statement (the "Registration Statement") on Form S-4, which
includes the Joint Proxy Statement and Prospectus relating to the Agreement and
Plan of Reorganization dated as of April 26, 2000 (the "Reorganization
Agreement") by and among Komag, Incorporated, a Delaware corporation ("Parent"),
KHM, Inc., a Delaware corporation and wholly owned subsidiary of Parent ("Merger
Sub"), and HMT Technology Corp., 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 the Company 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 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 or 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:



   2
Page 2


     (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 shareholders 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 Tax Representation Letters are
performed without waiver or breach of any material provision thereof;

     (d)  The Merger will be consummated in accordance with the terms of the
Reorganization Agreement without any waiver, breach, or amendment of any
covenant, condition or other provision thereof;

     (e)  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;

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

     (g)  The opinion dated _________, 2000 rendered by Wilson Sonsini Goodrich
& Rosati, P.C. to Parent has been delivered and has not been withdrawn.

Based on our examination of the foregoing items and subject to the assumptions,
exceptions, limitations and qualifications set forth herein, we are of the
opinion that the statements regarding United States federal income tax
consequences set forth in the Registration Statement under the heading "Material
United States Federal Income Tax Considerations of the Merger," insofar as they
constitute statements of law or legal conclusions, are correct in all material
respects. We express no opinion as to any federal, state or local, foreign or
other tax consequences, other than as set forth in the Registration Statement
under the heading "Certain Federal Income Tax Considerations."

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 may be relevant to a particular investor
in light of personal circumstances or to certain types of


   3
Page 3


investors subject to special treatment under the federal income tax laws (for
example, life insurance companies, dealers in securities, taxpayers subject to
the alternative minimum tax, banks, tax-exempt organizations, non-United States
persons, and shareholders who acquired their shares of Company capital stock
pursuant to the exercise of options or otherwise as compensation or who hold
their Company capital stock as part of a straddle or risk reduction
transaction).

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 intended solely for the purpose of inclusion as an exhibit to
the Registration Statement. It may not be relied upon or utilized for any other
purpose or by any person other than you and your shareholders and may not be
made available to any other person without our prior written consent. We hereby
consent to the filing of this opinion as an Exhibit to the Registration
Statement and to the reference to our firm under the heading "Legal Matters."

Sincerely,

/s/ Cooley Godward LLP



Robert H. Miller

RHM:tl