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                                                                     Exhibit 8.2

                            LOCKE LIDDELL & SAPP LLP
                           2200 Ross Avenue, Suite 220
                               Dallas, Texas 75201


                                 April 15, 1999



STB Systems, Inc.
3400 Waterview Parkway
Richardson, Texas 75080

Ladies and Gentlemen:

     We have acted as counsel to STB Systems, Inc., a Texas corporation (the
"Company") in connection with the proposed merger (the "Merger") of Voodoo
Merger Sub, Inc., a Texas corporation ("Sub") that is also a wholly owned
subsidiary of 3Dfx Interactive, Inc., a California corporation ("Parent"), with
and into the Company pursuant to the terms of that Agreement and Plan of
Reorganization dated as of December 13, 1998 (the "Merger Agreement") by and
among the Company, Parent and Sub. This opinion is being delivered to you in
connection with the registration statement of the Parent on Form S-4, filed with
the Securities and Exchange Commission on April 15, 1999 under the Securities
Act of 1933, as amended (the "Registration Statement"). This opinion is being
rendered pursuant to the requirements of Form S-4 under the Securities Act of
1933, as amended. Capitalized terms used hereunder but not defined have the
meanings ascribed to them in the Merger Agreement or the Registration Statement.

     In rendering this opinion we have examined and are relying upon such
documents (including all exhibits and schedules attached thereto) as we have
deemed relevant or necessary, including (i) the Merger Agreement, (ii) the
Registration Statement and (iii) such other documents as we have deemed
necessary or appropriate in order to enable us to render the opinion below, and
our opinion is conditioned upon (without any independent investigation or review
thereof) the truth and accuracy, at all relevant times, of the representations
and warranties, covenants and statements contained therein. This opinion is also
subject to and conditioned upon the receipt by counsel prior to the Effective
Time of the Merger of certain written tax representation letters (the "Tax
Representation Letters") of the Parent, Sub and the Company satisfactory to
counsel. The initial and continuing truth and accuracy of the representations
contained in these Tax Representation Letters constitutes an integral basis for
the opinion expressed herein and this opinion is conditioned upon the initial
and continuing truth and accuracy of these representations.

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STB Systems
April 15, 1999
Page 2


     In rendering this opinion, we have assumed that (without any independent
investigation or review thereof), and our opinion is conditioned on the
correctness of, the following: (i) each original document submitted to us
(including signatures thereto) is authentic, each document submitted to us as a
copy conforms to the original documents, and 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; (ii) all
representations, warranties and statements made or agreed to in connection with
the Merger by the Company, Parent and Sub, their managements, employees,
officers, directors and shareholders, including, but not limited to, those set
forth in the Merger Agreement (including the exhibits thereto) and the Tax
Representation Letters are true and accurate at all relevant times; (iii) all
covenants contained in the Merger Agreement (including exhibits thereto) and the
Tax Representation Letters are performed without waiver or breach of any
material provision thereof; (iv) the Merger will be reported by the Company,
Parent and Sub on their respective federal income tax returns in a manner
consistent with the opinion set forth below; and (v) any representation or
statement made "to the best of knowledge" or similarly qualified is correct
without such qualification. We also have assumed in connection with rendering
this opinion that the Merger will be consummated in accordance with the Merger
Agreement (and without any waiver, breach or amendment of any of the provisions
thereof).

     Based on our examination of the foregoing items and subject to the
limitations, qualifications, assumptions and caveats set forth herein, we are of
the opinion that:

     (i)   For United States federal income tax purposes the Merger will
           constitute a reorganization within the meaning of Section
           368(a)(1)(A) of the Internal Revenue Code of 1986, as amended (the
           "Code").

     (ii)  No gain or loss will be recognized by holders of Company common stock
           solely upon their receipt of Parent common stock solely in exchange
           for Company common stock in the Merger, except to the extent of cash
           received in lieu of a fractional share of Parent common stock.

     (iii) The aggregate tax basis of Parent common stock received by Company
           shareholders in the Merger will be the same as the aggregate tax
           basis of Company common stock surrendered in exchange therefore 
           reduced by any amount allocable to a fractional share interest for
           which cash is received.

     (iv)  The holding period of Parent common stock received in the merger will
           include the period for which the Company common stock surrendered in
           exchange therefor was held, provided that the Company common stock is
           held as a capital asset at the time of the Merger.

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STB Systems
April 15, 1999
Page 3


     (v)   Cash payments received by holders of Company common stock in lieu of
           a fractional share will be treated as if a fractional share of
           Parent common stock had been issued in the Merger and then redeemed
           by Parent. A shareholder of Company receiving such cash will
           generally recognize gain or loss upon such payment, equal to the
           difference, if any, between such shareholder's allocable basis in
           the fractional share and the amount of cash received. This gain or
           loss will be a capital gain or loss if the Company common stock is
           held by such shareholder as a capital asset at the effective time of
           the Merger.

     (vi)  Neither Parent, Sub nor Company will recognize gain or loss solely as
           a result of the merger.

     We express no opinion as to the various state, local or foreign tax
consequences that may result from the Merger or the other transactions
contemplated by the Merger Agreement. In addition, no opinion is expressed as to
any tax consequence of the Merger or the other transactions contemplated by the
Merger Agreement or other transactions effectuated prior or subsequent to or
concurrently with the Merger except as specifically set forth herein, and this
opinion may not be relied upon except with respect to the consequences
specifically discussed herein.

     We express no opinion as to any transactions whatsoever if any of the
transactions described in the Merger Agreement are not consummated in accordance
with the terms of the Merger Agreement and without waiver of any material
provision therein. If any of the representations, warranties, covenants
statements and assumptions upon which we have relied is not true and accurate at
all relevant times, our opinion may be adversely affected and should not be
relied upon.

     This opinion only represents our best judgment as to the probable Federal
income tax consequences of the Merger and is not binding on the Internal Revenue
Service or the courts or any other government body. The conclusions stated
herein are based on the Internal Revenue Code of 1986, as amended, and existing
judicial decisions, administrative regulations and published rulings. No
assurance can be given that future legislative, judicial or administrative
changes 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 tax laws.


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STB Systems
April 15, 1999
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     This opinion is furnished to you for the purpose of complying with
applicable securities laws. This opinion may not be used or relied upon by any
other person or for any other purpose and may not be circulated, quoted or
otherwise referred to for any purpose without our prior written consent. We
hereby consent to the use of this opinion as an exhibit to the Registration
Statement and to the reference to our Firm in the Registration Statement under
the captions "The Merger and Related Transactions - Material Federal Income Tax
Matters" and "Legal Matters."

                                       Sincerely,

                                       /s/ Locke Liddell & Sapp LLP
                                       ----------------------------
                                       LOCKE LIDDELL & SAPP LLP
