EXHIBIT (a)(1)(E)
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF

                               IKOS SYSTEMS, INC.
                                       AT
                              $11.00 NET PER SHARE
                                       BY

                              FRESNO CORPORATION,
                          A WHOLLY-OWNED SUBSIDIARY OF

                          MENTOR GRAPHICS CORPORATION

THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON
            TUESDAY, JANUARY 8, 2002, UNLESS THE OFFER IS EXTENDED.

To Our Clients:

     Enclosed for your consideration are the Offer to Purchase dated December 7,
2001 and the related Letter of Transmittal (which together, as amended,
supplemented or otherwise modified from time to time constitute the "Offer") in
connection with the offer by Mentor Graphics Corporation, an Oregon corporation
("Mentor") through Fresno Corporation, a Delaware corporation ("Purchaser"), and
a wholly-owned subsidiary of Mentor, to purchase for cash all of the shares of
common stock, par value $0.01 per share (the "Shares"), of IKOS Systems, Inc., a
Delaware corporation (the "Company"), including the associated preferred stock
purchase rights (the "Rights") issued pursuant to the Amended and Restated
Rights Agreement dated January 22, 1999 between the Company and Bank Boston,
N.A., as amended (the "Rights Agreement"). We are the holder of record of Shares
held for your account. A tender of such Shares and the associated Rights can be
made only by us as the holder of record and pursuant to your instructions. The
Letter of Transmittal is furnished to you for your information only and cannot
be used by you to tender Shares and Rights held by us for your account.

     We request instructions as to whether you wish us to tender any or all of
the Shares and Rights held by us for your account, upon the terms and subject to
the conditions set forth in the Offer to Purchase and the Letter of Transmittal.

     Your attention is invited to the following:

          1.  The tender price is $11.00 per Share, net to you in cash.

          2.  The Offer and withdrawal rights expire at 12:00 Midnight, New York
     City time, on Tuesday, January 8, 2002, unless the Offer is extended.

          3.  The Offer is conditioned upon, among other things, the following:

              - That the Company's stockholders validly tender and do not
                withdraw prior to the expiration date of the Offer a number of
                Shares (including the associated Rights) representing, together
                with the Shares owned by Mentor, at least a majority of the
                total number of outstanding Shares on a fully diluted basis.

              - That Mentor is satisfied, in its sole discretion, that the
                Agreement and Plan of Merger and Reorganization dated July 2,
                2001 among the Company, Synopsys, Inc. and Oak Merger


                Corporation (the "Synopsys Agreement") has been terminated in
                accordance with the terms of such agreement as in effect on the
                date of the Offer or such other terms as may be satisfactory to
                Mentor in its sole discretion.

              - That the termination fee provision in the Synopsys Agreement has
                been invalidated or the obligations to pay any amounts pursuant
                to such provision have been terminated, without any termination
                fee, or any portion thereof, having been paid by the Company or
                any of its affiliates pursuant to the Synopsys Agreement.

              - That the board of directors of the Company redeems the Rights in
                accordance with the terms of such Rights as in effect at such
                time or Mentor is satisfied, in its sole discretion, that the
                Rights have been invalidated or are otherwise inapplicable to
                the Offer and the Proposed Merger of Purchaser with and into the
                Company (the "Proposed Merger").

              - That Mentor is satisfied, in its sole discretion, that the
                provisions of Section 203 of the Delaware General Corporation
                Law do not apply to or otherwise restrict the Offer and the
                Proposed Merger.

              - That the Company's stockholders do not approve the Synopsys
                Agreement.

              - That the Company has not entered into or effectuated any
                agreement or transaction with any person or entity having the
                effect of impairing Purchaser's ability to acquire the Company
                or otherwise diminishing the expected economic value to Mentor
                of the acquisition of the Company.

              - That any waiting periods under applicable antitrust laws have
                expired or have been terminated.

          4.  Any stock transfer taxes applicable to the sale of Shares and
     Rights to the Purchaser pursuant to the Offer will be paid by the
     Purchaser, except as otherwise provided in Instruction 6 of the Letter of
     Transmittal.

     If you wish to have us tender any or all of your Shares and Rights, please
so instruct us by completing, executing, detaching and returning to us the
instruction form on the detachable part hereof. An envelope to return your
instructions to us is enclosed. If you authorize tender of your Shares and
Rights, all such Shares and Rights will be tendered unless otherwise specified
on the detachable part hereof. Your instructions should be forwarded to us in
ample time to permit us to submit a tender on your behalf by the expiration of
the Offer.

     The Offer is not being made to, nor will tenders be accepted from or on
behalf of, holders of Shares and Rights in any jurisdiction in which the making
of the Offer or acceptance thereof would not be in compliance with the laws of
such jurisdiction.

     Payment for Shares and Rights purchased pursuant to the Offer will in all
cases be made only after timely receipt by Wilmington Trust Company (the
"Depositary") of (a) certificates representing the Shares and Rights tendered or
timely confirmation of the book-entry transfer of such Shares and Rights into
the account maintained by the Depositary at The Depository Trust Company (the
"Book-Entry Transfer Facility"), pursuant to the procedures set forth in Section
4 of the Offer to Purchase, (b) the Letter of Transmittal, properly completed
and duly executed, with any required signature guarantees or an Agent's Message
(as defined in the Offer to Purchase), in connection with a book-entry delivery,
and (c) any other documents required by the Letter of Transmittal. Accordingly,
payment may not be made to all tendering stockholders at the same time depending
upon when certificates for or confirmations of book-entry transfer of such
Shares and Rights into the Depositary's account at the Book-Entry Transfer
Facility are actually received by the Depositary.

                                        2


                          INSTRUCTIONS WITH RESPECT TO
                           OFFER TO PURCHASE FOR CASH

                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF

                               IKOS SYSTEMS, INC.

     The undersigned acknowledge(s) receipt of your letter and the enclosed
Offer to Purchase dated December 7, 2001, and the related Letter of Transmittal,
in connection with the offer by Mentor through Purchaser to purchase all of the
shares of common stock, $0.01 par value per share (the "Shares"), of IKOS
Systems, Inc. (the "Company"), including the associated preferred stock purchase
rights (the "Rights) issued pursuant to the Amended and Restated Rights
Agreement, dated January 22, 1999, between the Company and Bank Boston, N.A., as
amended (the "Rights Agreement").

     This will instruct you to tender the number of Shares and Rights indicated
below held by you for the account of the undersigned, upon the terms and subject
to the conditions set forth in the Offer to Purchase and the related Letter of
Transmittal.

<Table>
<Caption>
- ---------------------------------------------   ---------------------------------------------
                                             
      Number of Shares to be Tendered:                            SIGN HERE


                                                ---------------------------------------------


- --------------------------------------- Shares* ---------------------------------------------
                                                                Signature(s)


      Number of Rights to be Tendered:          ---------------------------------------------
                                                        Please type or print name(s)


- --------------------------------------- Rights* ---------------------------------------------
                                                        Please type or print address

Dated
     ----------------------------------------   -----------------------------------------
                                                       Area Code and Telephone Number


                                                ---------------------------------------------
                                                         Taxpayer Identification or
                                                           Social Security Number
- ---------------------------------------------   ---------------------------------------------
</Table>

* Unless otherwise indicated, it will be assumed that all Shares and Rights held
  by us for your account are to be tendered.