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                        Quickturn Design Systems, Inc.
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                                                                   EXHIBIT 99.58


CONTACTS: 
        QUICKTURN DESIGN SYSTEMS, INC.      ABERNATHY MACGREGOR FRANK 
           Ray Ostby                          Pauline Yoshihashi 
           (408) 914-6000                     (213) 630-6550 
                                              Matt Sherman 
                                              (212) 371-5999 

FOR IMMEDIATE RELEASE 


             QUICKTURN COMMITTED TO STRATEGIC MERGER WITH CADENCE

SAN JOSE, Calif. December 15, 1998 -- Quickturn Design Systems, Inc. (Nasdaq:
QKTN) today responded to Mentor Graphic's latest maneuver in its desperate
attempt to try to acquire Quickturn through a hostile takeover. Quickturn
reiterated its commitment to its merger with Cadence Design Systems, Inc. (NYSE:
CDN). 

        Keith R. Lobo, president and chief executive officer of Quickturn,
said, "We are confident that our strategic merger with Cadence is in the best
interest of Quickturn and its stockholders. Our combination with Cadence
enables Quickturn stockholders to continue to participate in Quickturn's
future growth and to enjoy the added benefits of Cadence's proven business
strategy, strong balance sheet and excellent track record in acquiring and
integrating companies.

        Mentor's obtaining ownership of Quickturn's patents was the primary
motivation for its unsolicited takeover attempt. Now that Quickturn has agreed
to a strategic merger with Cadence at a superior value for Quickturn's
stockholders, Mentor is making a last ditch effort.

        On December 8, 1998, the Quickturn board of directors unanimously
approved a definitive merger agreement with Cadence under which Cadence will
acquire Quickturn in a tax-free, stock-for-stock transaction with an aggregate
purchase price of $253 million. Upon closing of the merger, each shareholder of
Quickturn will receive Cadence common stock with a value of $14 per share. As a
result of the merger, Quickturn will become a wholly-owned subsidiary of
Cadence.

        Quickturn Design Systems, Inc. is a leading provider of verification
hardware and time-to-market engineering (TtME/TM/) services for the design of
complex ICs and electronic systems. The company's products are used worldwide by
developers of high-performance computing, multimedia, graphics and
communications systems. Quickturn is headquartered in San Jose, Calif. For more
information, visit the Quickturn Web site at http://www.quickturn.com or send e-
mail to info@quickturn.com. 

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