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                        QUICKTURN DESIGN SYSTEMS, INC.
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CONTACTS:
      QUICKTURN DESIGN SYSTEMS, INC.            ABERNATHY MACGREGOR FRANK
      Raymond K. Ostby                          Pauline Yoshihashi/Matt Sherman
      Vice President-Finance & Administration   (213) 630-6550/(212) 371-5999
      (408) 914-6633

FOR IMMEDIATE RELEASE

               QUICKTURN SEEKS $225 MILLION CLAIM FOR DAMAGES
                            FROM MENTOR GRAPHICS

 QUICKTURN WINS FIFTH CONSECUTIVE ROUND IN MENTOR PATENT INFRINGEMENT BATTLE

SAN JOSE, Calif., -- October 5, 1998 -- Quickturn Design Systems, Inc. 
(Nasdaq: QKTN) announced today that it has submitted preliminary damage claims
in excess of $225 million in its U.S. District Court (Oregon) patent 
infringement lawsuit against Mentor Graphics Corporation (Nasdaq: MENT). This 
amount is comprised of at least $75 million of damage claims along with a 
request that the court award an additional $150 million of treble damages on 
the basis that Mentor willfully infringed Quickturn's patents. Willful 
infringement is grounds for a court to award up to treble damages in such 
cases. The trial is scheduled to begin December 1, 1998. The International 
Trade Commission (ITC) has already ruled that Mentor submitted "false and 
misleading" evidence in support of their defenses to the same Quickturn patents
and described Mentor's defenses as "thoughtless, reckless and harassing."

    Keith R. Lobo, Quickturn's president and chief executive officer, said, "We
believe that Mentor understands the full scope of their exposure in this case.
We believe that this exposure is the primary reason that they are trying to 
buy Quickturn with their unsolicited tender offer. If they are successful in 
their takeover bid, they will essentially be paying these damages to 
themselves instead of to Quickturn and its stockholders, to whom that money 
belongs."

    Quickturn also announced today that it won the fifth consecutive round in 
its continuing legal battle to stop Mentor from infringing Quickturn's 
intellectual property. On September 28, 1998, the U.S. Court of Appeals for 
the Federal Circuit denied Mentor's final appeal of the preliminary injunction
granted to Quickturn on August 1, 1997 by Judge Redden of the U.S. District 
Court (Oregon). This ruling reaffirms the Federal Circuit's August 5, 1998 
denial of Mentor's appeal of the Oregon District Court's preliminary 
injunction. Seven days after this denial, Mentor commenced its unsolicited 
takeover bid for Quickturn.

                                   -more-

 
                                     -2-

        Quickturn has been fighting Mentor since late 1995 in two U.S. 
courts and one German court to prevent Mentor from importing, selling, 
distributing or manufacturing certain hardware emulation systems and their 
components which have been found to infringe certain Quickturn patents.

        Quickturn has won every round in these cases during the three years 
since Mentor filed the initial suit attempting to invalidate certain Quickturn 
patents and asking the courts to declare that Mentor's products do not 
infringe those patents. These five rulings in Quickturn's favor have 
consistently upheld the validity of Quickturn's patents and have verified that
Mentor's hardware emulation systems infringe Quickturn's patents. These 
Quickturn wins have included: (1) the August 1996 Temporary Exclusion Order 
issued by the ITC; (2) the August 1997 denial of Mentor's appeal of the ITC's 
Temporary exclusion order; (3) the August 1997 Permanent Exclusion Order 
issued by the ITC which precludes Mentor from importing infringing products 
and components until 2009; (4) the August 1997 Preliminary Injunction issued 
by the U.S. District Court (Oregon) which precludes Mentor from manufacturing 
or selling their infringing products in the United States; and (5) the 
September 1998 denial of Mentor's appeal of the District Court's preliminary 
injunction.

        Quickturn Design Systems, Inc. is the leading provider of verification
products 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 at 55 W. Trimble Road, San 
Jose, CA 95131-1013; Telephone: 408/914-6000. For more information, visit the 
Quickturn Web site at www.quickturn.com or send e-mail to info@quickturn.com.


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