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                                  SCHEDULE 14A
                                 (RULE 14A-101)
 
                    INFORMATION REQUIRED IN PROXY STATEMENT
 
                            SCHEDULE 14A INFORMATION
          PROXY STATEMENT PURSUANT TO SECTION 14(A) OF THE SECURITIES
                    EXCHANGE ACT OF 1934 (AMENDMENT NO.   )
 
Filed by the Registrant [X]
 
Filed by a Party other than the Registrant [ ]
 
Check the appropriate box:
 

                                             
[ ]  Preliminary Proxy Statement                [ ]  Confidential, for Use of the Commission
                                                     Only (as permitted by Rule 14a-6(e)(2))
[ ]  Definitive Proxy Statement
[X]  Definitive Additional Materials
[ ]  Soliciting Material Pursuant to Rule 14a-11(c) or Rule 14a-12

                               STB Systems, Inc.
- --------------------------------------------------------------------------------
                (Name of Registrant as Specified In Its Charter)
 
- --------------------------------------------------------------------------------
    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)
 
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          pursuant to Exchange Act Rule 0-11 (set forth the amount on which the
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     As many of you know, 3dfx Interactive and STB Systems will be holding
special meetings of their shareholders tomorrow, Friday, April 30, 1999 to vote
on the proposed merger between the two companies and other related matters.

     The meetings were scheduled with a very short timeline in order to get the
vote completed before the end of this Fiscal Quarter. As a result of this
somewhat compressed timeframe, some shareholders have only recently received
their proxy statements and have not yet voted. Please note that if you have not
yet received your proxy statement, you should do the following immediately: for
3dfx shareholders, contact Paul Wilson at 408-935-4400; for STB shareholders,
contact Bryan Keyes at 972-234-8750.

     It is very important for both companies to receive your vote: 3dfx must
receive over fifty percent of its outstanding shares and STB must receive
two-thirds of their outstanding shares to obtain approval. If you were a
shareholder of 3dfx on March 26, 1999 or of STB on March 30, 1999, we need you
to send your vote in today -- Thursday, April 29, 1999 -- either by electronic
or telephonic means. Votes can be cast via the internet at "www.proxyvote.com"
or via telephone by dialing the 800# indicated on your voting instructions. You
will need your twelve-digit control number indicated on your proxy card in order
to log your vote.

     In closing, I want to thank you for your attention to this important
matter, to reconfim how much we value our shareholders, and to say how very
excited we are about the prospects for the combined company.