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                                                                    EXHIBIT 99.2
 
                               STB SYSTEMS, INC.
                   PROXY FOR SPECIAL MEETING OF SHAREHOLDERS
          THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS
 
    The undersigned shareholder of STB SYSTEMS, INC., a Texas corporation,
hereby acknowledges receipt of the Notice of Special Meeting of Shareholders and
Joint Proxy Statement/Prospectus, each dated April 19, 1999, and hereby appoints
William E. Ogle and Randall D. Eisenbach and each of them proxies and
attorneys-in-fact, with full power to each of substitution, on behalf and in the
name of the undersigned, to represent the undersigned at the Special Meeting of
Shareholders of STB SYSTEMS, INC., to be held on Friday, April 30, 1999 at 
1:00 p.m., local time, at the headquarters of STB at 3400 Waterview Parkway,
Richardson, Texas and any adjournment(s) thereof, and to vote all shares of
Common Stock which the undersigned would be entitled to vote if then and there
personally present, on the matters set forth on the reverse side.
 
    1.  Proposal to approve and adopt the Merger Agreement and to approve the
        Merger.
              [ ]  FOR             [ ]  AGAINST            [ ]  ABSTAIN
 
    In their discretion, the proxies are authorized to vote upon such other
matter(s) as may properly come before the meeting (including any motion to 
adjourn to a later time to permit further solicitation of proxies if necessary 
to establish a quorum or to obtain additional votes in favor of the proposal) 
or before any postponements or adjournments thereof.





 
                MARK HERE FOR ADDRESS CHANGE AND NOTE BELOW  [ ]
 
    THIS PROXY WILL BE VOTED AS DIRECTED OR, IF NO DIRECTION IS INDICATED, WILL
BE VOTED FOR THE APPROVAL AND ADOPTION OF THE MERGER AGREEMENT AND APPROVAL OF 
THE MERGER.
 
    Both of such attorneys or substitutes (if both are present and acting at
said meeting or any adjournment(s) thereof, or, if only one shall be present and
acting, then that one) shall have and may exercise all of the powers of said
attorneys-in-fact hereunder.
 
                                           Dated:
 
                                           -------------------------------------
                                                         Signature
 
                                           -------------------------------------
                                                         Signature
 
    THIS PROXY SHOULD BE MARKED, DATED, SIGNED BY THE SHAREHOLDER(S) EXACTLY AS
HIS OR HER NAME APPEARS HEREON, AND RETURNED PROMPTLY IN THE ENCLOSED ENVELOPE.
PERSONS SIGNING IN A FIDUCIARY CAPACITY SHOULD SO INDICATE. IF SHARES ARE HELD
BY JOINT TENANTS OR AS COMMUNITY PROPERTY, BOTH SHOULD SIGN.
