<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
------------------------
AMENDMENT NO. 18
TO SCHEDULE 14D-1
TENDER OFFER STATEMENT
(PURSUANT TO SECTION 14(D)(1) OF THE SECURITIES EXCHANGE ACT OF 1934)
QUICKTURN DESIGN SYSTEMS, INC.
(Name of Subject Company)
MENTOR GRAPHICS CORPORATION
MGZ CORP.
(Bidders)
COMMON STOCK, PAR VALUE $.001 PER SHARE
(including the Associated Rights)
(Title of Class of Securities)
74838E102
(CUSIP Number of Class of Securities)
------------------------
WALDEN C. RHINES
PRESIDENT AND CHIEF EXECUTIVE OFFICER
MENTOR GRAPHICS CORPORATION
8005 S.W. BOECKMAN ROAD
WILSONVILLE, OREGON 97070-7777
(503) 685-1200
(Name, Address and Telephone Number of Persons Authorized
to Receive Notices and Communications on Behalf of Bidders)
COPY TO:
JOHN J. HUBER, ESQ. CHRISTOPHER L. KAUFMAN, ESQ.
LATHAM & WATKINS LATHAM & WATKINS
1001 PENNSYLVANIA AVENUE, N.W. 75 WILLOW ROAD
WASHINGTON, DC 20004 MENLO PARK, CALIFORNIA 94025
(202) 637-2200 (650) 328-4600
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
MGZ Corp., a Delaware corporation ("Purchaser"), and Mentor Graphics
Corporation, an Oregon corporation ("Parent"), hereby amend and supplement their
Tender Offer Statement on Schedule 14D-1 filed on August 12, 1998 (the
"Statement"), as amended, with respect to the offer by Purchaser to purchase all
outstanding shares of Common Stock, par value $.001 per share, of Quickturn
Design Systems, Inc., a Delaware corporation, for a purchase price of $12.125
per share, net to the seller in cash, without interest thereon, as set forth in
this Amendment No. 18. Capitalized terms used herein and not defined have the
meanings ascribed to them in the Statement.
ITEM 10. ADDITIONAL INFORMATION.
Item 10(f) of the Statement is hereby amended and supplemented by the
following:
1. On October 29, 1998, Parent issued a press release, a copy of which is
attached hereto as Exhibit (a)(36) and is incorporated herein by reference.
ITEM 11. MATERIAL TO BE FILED AS EXHIBITS.
(a)(36) Press Release dated October 29, 1998.
2
<PAGE>
SIGNATURES
After due inquiry and to the best of my knowledge and belief, I certify that
the information set forth in this statement is true, complete and correct.
<TABLE>
<S> <C> <C>
Dated: October 29, 1998 MENTOR GRAPHICS CORPORATION
By: /s/ GREGORY K. HINCKLEY
--------------------------------------
Name Gregory K. Hinckley
Title: Executive Vice President, Chief Operating
Officer and Chief Financial Officer
MGZ CORP.
By: /s/ GREGORY K. HINCKLEY
--------------------------------------
Name: Gregory K. Hinckley
Title: Secretary and Chief Financial Officer
</TABLE>
3
<PAGE>
MENTOR GRAPHICS SAYS SPECIAL MEETING OF QUICKTURN
STOCKHOLDERS CONVENED AND ADJOURNED TO NOVEMBER 24
-- QUICKTURN STOCKHOLDERS URGED TO TENDER SHARES ON OR BEFORE
OCTOBER 30 EXPIRATION DATE --
WILSONVILLE, OR, OCTOBER 29, 1998 -- Mentor Graphics Corporation (Nasdaq:
MENT) announced that, pursuant to an agreement with Quickturn Design Systems,
Inc. (Nasdaq: QKTN), the special meeting of Quickturn stockholders called by
Mentor Graphics convened today and was immediately adjourned until November
24, 1998 without conducting any substantive business. The record date for
the November 24, 1998 special meeting called by Mentor continues to be
September 10, 1998.
As previously announced, the principal purpose of the special meeting is to
vote on replacing the current members of the Quickturn Board of Directors
with a slate of independent directors nominated by Mentor Graphics. If the
nominees are elected, Mentor Graphics expects that, subject to their
fiduciary duties to all Quickturn stockholders, the new directors will take
the steps necessary to facilitate the stockholders' ability to accept Mentor
Graphics' $12.125 per share all-cash offer. Quickturn continues to assert,
nevertheless, that the special meeting date has been conditionally set for
January 8, 1999, citing a bylaw that it purported to adopt after Mentor
Graphics' offer commenced on August 12, 1998.
Dr. Walden C. Rhines, President and Chief Executive Officer of Mentor
Graphics, said: "We look forward to the November 24 special meeting, and in
the meantime urge Quickturn stockholders to tender their shares before the
expiration of Mentor's Offer at 12:00 Midnight, New York City time, on
Friday, October 30, 1998, unless extended. Tendering shares is the best way
for Quickturn stockholders to send a message to the Quickturn Board of
Directors to end their entrenchment tactics."
Separately, the trial in which Mentor Graphics challenged the validity of the
<PAGE>
bylaw and poison pill amendments adopted by Quickturn after Mentor Graphics
commenced its $12.125 per share all-cash offer on August 12, 1998, ended
Wednesday afternoon in Delaware Court of Chancery. Mentor Graphics expects
that post-trial briefs from both sides will be completed by November 6, 1998,
and a decision by the Court of Chancery is expected shortly thereafter.
Mentor Graphics' Offer to Purchase and ancillary documents are available on a
Mentor Graphics World Wide Web site at http://www.mentorg.com/file.
The Dealer Manager for the Offer is Salomon Smith Barney. The Information
Agent for the Offer is MacKenzie Partners, Inc., which can be reached
toll-free at 800-322-2885 or by collect call at 212-929-5500.
CONTACT: Anne M. Wagner Roy Winnick/Todd Fogarty
Vice President, Marketing Kekst and Company
503/685-1462 212/521-4800
# # #