<PAGE>

                                                                         [LOGO]

ROSS A. BEATON
VICE PRESIDENT
OREGON CORPORATE BANKING

111 S.W. Fifth Avenue, Suite 400
Portland, OR 97204
503-275-6350
503-273-5795 Fax

April 30, 1998

Art Fletcher
Treasurer and Director of Financial Planning
Summit Design, Inc.
9305 S.W. Gemini Drive
Beaverton, OR 97005-7158

Gentlemen:

I am pleased to advise you that United States National Bank of Oregon ("Bank")
has approved the request of Summit Design, Inc. ("Summit"), for the following
credit facilities, subject to the following terms and conditions:

                          OPERATING LINE OF CREDIT

BORROWER:          Summit Design, Inc.

PURPOSE:           General Corporate Purposes.

BORROWING LIMIT:   $1,000,000.00

GUARANTORS:        None

EXPIRY:            April 30, 1999.

RATE:              Pricing will be based on United States National Bank 
                   of Oregon's Prime(l), or London Interbank Offering Rate 
                   ("LIBOR"), at the Borrower's option.  Rate will be fully 
                   floating and computed on a 360-day year.  The spread over 
                   the base rates will be determined quarterly by the 
                   Borrower's Total Liabilities/Tangible Net Worth "D/TNW"), 
                   as expressed in the chart below.



------------------------
1    The interest rate charged to Borrower is tied to the Prime Rate of United
     States National Bank of Oregon, Borrower is advised that United States 
     National Bank's Prime Rate is the rate of interest which the Bank from 
     time to time identifies and publicly announces as its Prime Rate, and is 
     not necessarily, for example the lowest rate of interest which the Bank 
     collects from any borrower or group of borrowers.

<PAGE>

Summit Design, Inc.
4/30/1998
Page 2


                 DEBT TO TANGIBLE NET WORTH IS DEFINED AS (TOTAL 
                 LIABILITIES MINUS UNEARNED REVENUE)/(SHAREHOLDERS'
                 EQUITY MINUS INTANGIBLES).

<TABLE>
<CAPTION>
           -----------------------------------------------------------
               DEBT/WORTH         PRIME PRICING   LIBOR PRICING
           -----------------------------------------------------------
           <S>                    <C>             <C>
              Greater than 0.50   Prime + 0%      LIBOR + 225 bps
                .26 to .050       Prime + 0%*     LIBOR + 200 bps
               Less than 0.26     Prime + 0%      LIBOR + 150 bps.
           -----------------------------------------------------------
</TABLE>
                               * At 12/31/97 the D/TNW was 0.66:1.00.
                                  (Overall LIBOR spreads have been reduced by 
                                  75 basis points, and Prime spreads have been 
                                  eliminated from the existing facility.)

                 LIBOR Terms:

                 A) Minimum Amount of $500,000, increments of $100,000
                    thereafter.

                 B) Maturity and availability: Up to three months; may not 
                    exceed Expiry.

                 C) Prepayment of LIBOR Borrowings not permitted.

                 D) Notification: Two day notification prior to 12:00 noon on 
                    the day of notification.

                 E) Irrevocability: Acceptance of a pricing commitment from 
                    the Bank will constitute an irrevocable agreement to borrow 
                    under the revolving line of credit.

                 F) Interest computed on the basis of a 360 day year and the
                    number of days elapsed.

REPAYMENT TERMS: Interest shall be payable monthly on the 1st day of each 
                 month.  Principal shall be payable on the earlier of April 
                 30, 1999, or demand by the Bank.  Repayment of each advance 
                 received by Borrower under the line of credit is subject to 
                 the terms of the promissory note evidencing that advance, as 
                 well as all terms and conditions of this letter.  In the 
                 event of any conflict between the two, the terms and 
                 conditions of the promissory note shall control.

FEES:            UP-FRONT FEE:    Initial up-front fee of 1/8 of 1% of the 
                 amount of the line of credit, due upon acceptance ($1,250).

                 COMMITMENT FEE:  A 1/8 of 1% fee, annualized, on the unused 
                 portion of the line of credit, payable quarterly in arrears.

<PAGE>


Summit Design, Inc.
4/30/1998
Page 3


COLLATERAL:      The revolving line of credit provides for a flexible 
                 collateral position according to the following matrix.  The 
                 assets of the Borrower which are referenced below include a 
                 first lien position in all accounts, contract rights, 
                 chattel paper, general intangibles and inventory.


QUICK RATIO*     COLLATERAL

 GREATER THAN 
  1.75:1.00      Unsecured with negative pledge agreement.

 LESS THAN OR =
  1.75:1.00      UNSECURED WITH NEGATIVE PLEDGE, IF NOT BORROWING.  If borrowing
                 and the ratio falls in this category, the line of credit will 
                 be secured.

 LESS THAN OR =  
  1.25:1.00      UNSECURED WITH NEGATIVE PLEDGE, IF NOT BORROWING.  If
                 borrowing, line is secured and advances are margined at 75% 
                 of eligible A/R up to 120 days after date of invoice.

                 * QUICK RATIO IS DEFINED AS ((CASH + NET TRADE ACCOUNTS)/
                   (CURRENT LIABILITIES - CURRENT PORTION OF UNEARNED REVENUE)).

DOCUMENTATION:   Execution of Notes, Loan Agreements, Security Agreements, 
                 UCC Financing Statements and all other documentation 
                 required by the Bank in a form satisfactory to the Bank.

BORROWER WILL COMPLY WITH THE FOLLOWING QUARTERLY FINANCIAL COVENANTS:

                 1. TANGIBLE NET WORTH shall not be less then $10,000,000.  
                    TANGIBLE NET WORTH IS DEFINED AS (SHAREHOLDER'S EQUITY -
                    INTANGIBLES).  NOTE: INTANGIBLES INCLUDE ALL CAPITALIZED
                    SOFTWARE.

                 2. TOTAL LIABILITIES TO TANGIBLE NET WORTH shall not exceed 
                    .75 to 1.00. TOTAL LIABILITIES TO TANGIBLE NET WORTH IS 
                    DEFINED AS (TOTAL LIABILITIES MINUS DEFERRED 
                    REVENUE)/(TANGIBLE NET WORTH).

                 Failure to maintain these covenants will be considered an 
                 event of default under the loan documents.

<PAGE>

Summit Design, Inc.
4/30/1998
Page 4


REPORTING REQUIREMENTS:

                 -  Quarterly financial statements to be submitted within 45 
                    days of quarter end.

                 -  Annual CPA audited financial statements to be submitted 
                    within 90 days of fiscal year end.

                 -  If the Quick Ratio falls to 1.25:1.00 or below: A 
                    Borrower's Certificate will be submitted with each advance,
                    and a Borrower's Certificate will accompany the monthly AR 
                    and AP agings.

ADVANCE 
 STRUCTURE:      Advances will be limited to the Borrowing Limit when the
                 Quick Ratio is greater than 1.25:1.00. When the quick ratio 
                 is less than or equal to 1.25:1.00, advances will be 
                 limited to 75% of eligible accounts receivable to 120 days 
                 after the date of invoice.

                 Disbursements under the line of credit shall terminate on the 
                 earlier occurrence of the date indicated above as the Expiry 
                 Date or the date on which this Bank, in its sole discretion, 
                 determines that there has been a material adverse change in 
                 the financial condition or management of the Borrower, or 
                 determines that there has been any non-compliance with any 
                 term or condition stated herein.  Non-compliance with the 
                 conditions and terms of this letter and all other loan 
                 documents will be considered as an event of default, 
                 entitling the Bank to all the default provisions as provided 
                 for in documents evidencing this line of credit.




If the above terms and conditions to extend this credit facility to Summit
Design, Inc. are acceptable to you, please sign and return the Acknowledgment
Copy of this letter on or before May 15, 1998.

<PAGE>

Summit Design, Inc.
4/30/1998
Page 5


We are pleased to provide you this borrowing accommodation and look forward to
serving your banking needs in the future.

Sincerely,

/s/ Ross A. Beaton

Ross A. Beaton
Vice President


BY OREGON STATUTE (ORS 41.580), THE FOLLOWING DISCLOSURE IS REQUIRED: UNDER
OREGON LAW MOST AGREEMENTS PROMISES AND COMMITMENTS MADE BY LENDERS AFTER
OCTOBER 3, 1989 CONCERNING LOANS AND OTHER CREDIT EXTENSIONS WHICH ARE NOT FOR
PERSONAL, FAMILY, OR HOUSEHOLD PURPOSE OR SECURED SOLELY BY THE BORROWER'S
RESIDENCE MUST BE IN WRITING, EXPRESS CONSIDERATION AND BE SIGNED BY THE LENDER
TO BE ENFORCEABLE.


THE UNDERSIGNED HEREBY ACKNOWLEDGES AND ACCEPTS THIS OFFER TO EXTEND CREDIT
SUBJECT TO THE TERMS AND CONDITIONS STATED ABOVE.

SUMMIT DESIGN, INC.

BY: /s/ C. Albert Koob      CFO                       4/30/98
    -----------------------------               -------------------------
                           Title                Date


<PAGE>

                            ALTERNATIVE RATE OPTIONS
                                PROMISSORY NOTE
                              (PRIME RATE, LIBOR)

$1,000,000.00                                                Dated as of: 5/1/98

 Summit Design, Inc.                                                ("Borrower")

U.S. BANK NATIONAL ASSOCIATION                                        ("Lender")

1.   TYPE OF CREDIT.  This note is given to evidence Borrower's obligation to 
repay all sums which Lender may from time to time advance to Borrower 
(Advances") under a:

 / / single disbursement loan.  Amounts loaned to Borrower hereunder will be 
     disbursed in a single Advance in the amount shown in Section 2.

 /X/ revolving line of credit.  No Advances shall be made which create a 
     maximum amount outstanding at any one time which exceeds the maximum 
     amount shown in Section 2. However, Advances hereunder may be borrowed, 
     repaid and reborrowed, and the aggregate Advances loaned hereunder from 
     time to time may exceed such maximum amount.

 / / non-revolving line of credit.  Each Advance made from time to time 
     hereunder shall reduce the maximum amount available shown in Section 2. 
     Advances loaned hereunder which are repaid may not be reborrowed.

2.   PRINCIPAL BALANCE.  The unpaid principal balance of all Advances 
outstanding under this note ('Principal Balance") at one time shall not 
exceed $1,000,000.00 .

3.   PROMISE TO PAY.  For value received Borrower promises to pay to Lender 
or order at COMMERCIAL LOAN SERVICING the Principal Balance of this note, with 
interest thereon at the rate(s) specified in Sections 4 and 11 below.

4.   INTEREST RATE.  The interest rate on the Principal Balance outstanding 
may vary from time to time pursuant to the provisions of this note.  Subject 
to the provisions of this note, Borrower shall have the option from time to 
time of choosing to pay interest at the rate or rates and for the applicable 
periods of time based on the rate options provided herein; PROVIDED, however, 
that once Borrower notifies Lender of the rate option chosen in accordance 
with the provisions of this note, such notice shall be irrevocable.  The rate 
options are the Prime Borrowing Rate and the LIBOR Borrowing Rate, each as 
defined herein.

(a)  Definitions.  The following terms shall have the following meanings:

            "Business Day" means any day other than a Saturday, Sunday, or 
other day that commercial banks in Portland, Oregon or New York City are 
authorized or required by law to close; provided, however that when used in 
connection with a LIBOR Rate, LIBOR Amount or LIBOR Interest Period such term 
shall also exclude any day on which dealings in U.S. dollar deposits are not 
carried on in the London interbank market.

            "LIBOR Amount" means each principal amount for which Borrower 
chooses to have the LIBOR Borrowing Rate apply for any specified LIBOR 
Interest Period.

            "LIBOR Interest Period" means as to any LIBOR Amount, a period of 
ONE, TWO OR THREE months commencing on the date the LIBOR Borrowing Rate 
becomes applicable thereto; PROVIDED, however, that: (i) the first day of 
each LIBOR Interest Period must be a Business Day; (ii) no LIBOR Interest 
Period shall be selected which would extend beyond EXPIRY; (iii) no LIBOR 
Interest Period shall extend beyond the date of any principal payment 
required under Section 6 of this note, unless the sum of the Prime Rate 
Amount, plus LIBOR Amounts with LIBOR Interest Periods ending on or before 
the scheduled date of such principal payment, plus principal amounts 
remaining unborrowed under a line of credit, equals or exceeds the amount of 
such principal payment; (iv) any LIBOR Interest Period which would otherwise 
expire on a day which is not a Business Day, shall be extended to the next 
succeeding Business Day, unless the result of such extension would be to 
extend such LIBOR Interest Period into another calendar month, in which event 
the LIBOR Interest Period shall end on the immediately preceding Business 
Day; and (v) any LIBOR Interest Period that begins on the last Business Day of 
a calendar month (or on a day for which there is no numerically corresponding 
day in the calendar month at the end of such LIBOR Interest Period) shall end 
on the last Business Day of a calendar month.

            "LIBOR Rate" means, for any LIBOR Interest Period, the rate per 
annum (computed on the basis of a 360-day year and the actual number of days 
elapsed and rounded upward to the nearest 1/16 of 1 %) established by Lender 
as its LIBOR Rate, based on Lenders determination, on the basis of such 
factors as Lender deems relevant, of the rate of interest at which U.S. 
dollar deposits would be offered to U.S. Bank National Association in the 
London interbank market at approximately 11 a.m. London time on the date 
which is two Business Days prior to the first day of such LIBOR Interest 
Period for delivery on the first day of such LIBOR Interest Period for the 
number of months therein; provided, however, that the LIBOR Rate shall be 
adjusted to take into account the maximum reserves required to be maintained 
for Eurocurrency liabilities by banks during each such LIBOR Interest Period 
as specified in Regulation D of the Board of Governors of the Federal Reserve 
System or any successor regulation.

            "Prime Rate" means the rate of interest which Lender from time to 
time establishes as its prime rate and is not, for example, the lowest rate 
of interest which Lender collects from any borrower or class of borrowers.  
When the Prime Rate is applicable under Section 4(b) or 11(b), the interest 
rate hereunder shall be adjusted without notice effective on the day the 
Prime Rate changes, but in no event shall the rate of interest be higher than 
allowed by law.

            "Prime Rate Amount" means any portion of the Principal Balance 
bearing interest at the Prime Borrowing Rate.

(b)  THE PRIME BORROWING RATE.

     (i)    The Prime Borrowing Rate is a per annum rate equal to the Prime 
Rate plus SEE ATTACHED EXHIBIT "A"% per annum.

     (ii)   Whenever Borrower desires to use the Prime Borrowing Rate option, 
Borrower shall give Lender notice orally or in writing in accordance with 
Section 15 of this note, which notice shall specify the requested effective 
date (which must be a Business Day) and principal amount of the Advance or 
increase in the Prime Rate Amount, and whether Borrower is requesting a new 
Advance under a line of credit or conversion of a LIBOR Amount to the Prime 
Borrowing Rate.

     (iii)  Subject to Section 11 of this note, interest shall accrue on the 
unpaid Principal Balance at the Prime Borrowing Rate unless and except to the 
extent that the LIBOR Borrowing Rate is in effect.

(c)  THE LIBOR BORROWING RATE.

     (i)    The LIBOR Borrowing Rate is the LIBOR Rate plus SEE ATTACHED 
EXHIBIT "A"% per annum.

     (ii)   Borrower may obtain LIBOR Borrowing Rate quotes from Lender 
between 8:00 a.m. and 10:00 a.m. (Portland, Oregon time) on any Business Day. 
Borrower may request an Advance, conversion of any portion of the Prime Rate 
Amount to a LIBOR Amount or a new LIBOR Interest Period for an existing LIBOR 
Amount, at such rate only by giving Lender notice in accordance with Section 
4 (c)(iii) before 10:00 a.m. (Portland, Oregon time) on such day.


                                                                     Page 1 of 4

<PAGE>

     (iii)  Whenever Borrower desires to use the LIBOR Borrowing Rate option, 
Borrower shall give Lender irrevocable notice (either in writing or orally 
and promptly confirmed in writing) between 8:00 a.m. and 10:00 a.m. 
(Portland, Oregon time) two (2) Business Days prior to the desired effective 
date of such rate. Any oral notice shall be given by, and any written notice 
or confirmation of an oral notice shall be signed by, the person(s) authorized 
in Section 15 of this note, and shall specify the requested effective date of 
the rate, LIBOR Interest Period and LIBOR Amount, and whether Borrower is 
requesting a new Advance at the LIBOR Borrowing Rate under a line of credit, 
conversion of all or any portion of the Prime Rate Amount to a LIBOR Amount, 
or a new LIBOR Interest Period for an outstanding LIBOR Amount. 
Notwithstanding any other term of this note, Borrower may elect the LIBOR 
Borrowing Rate in the minimum principal amount of $500,000.00 and in 
multiples of $100,000.00 above such amount; PROVIDED, however, that no more 
than N/A separate LIBOR Interest Periods may be in effect at any one time.

     (iv)   If at any time the LIBOR Rate is unascertainable or unavailable 
to Lender or if LIBOR Rate loans become unlawful, the option to select the 
LIBOR Borrowing Rate shall terminate immediately. If the LIBOR Borrowing Rate 
is then in effect, (A) it shall terminate automatically with respect to all 
LIBOR Amounts (i) on the last day of each then applicable LIBOR Interest 
Period, if Lender may lawfully continue to maintain such loans, or (ii) 
immediately if Lender may not lawfully continue to maintain such loans 
through such day, and (B) subject to Section 11, the Prime Borrowing Rate 
automatically shall become effective as to such amounts upon such termination.

     (v)    If at any time after the date hereof (A) any revision in or 
adoption of any applicable law, rule, or regulation or in the interpretation 
or administration thereof (i) shall subject Lender or its Eurodollar lending 
office to any tax, duty, or other charge, or change the basis of taxation of 
payments to Lender with respect to any loans bearing interest based on the 
LIBOR Rate, or (ii) shall impose or modify any reserve, insurance, special 
deposit, or similar requirements against assets of, deposits with or for the 
account of, or credit extended by Lender or its Eurodollar lending office, or 
impose on Lender or its Eurodollar lending office any other condition 
affecting any such loans, and (B) the result of any of the foregoing is (i) 
to increase the cost to Lender of making or maintaining any such loans or 
(ii) to reduce the amount of any sum receivable under this note by Lender or 
its Eurodollar lending office, Borrower shall pay Lender within 15 days after 
such demand by Lender such additional amount as will compensate Lender for 
such increased cost or reduction. The determination hereunder by Lender of 
such additional amount shall be conclusive in the absence of manifest error. 
If Lender demands compensation under this Section 4(c)(v), Borrower may upon 
three (3) Business Days' notice to Lender pay the accrued interest on all 
LIBOR Amounts, together with any additional amounts payable under Section 
4(c)(vi). Subject to Section 11, upon Borrower's paying such accrued interest 
and additional costs, the Prime Borrowing Rate immediately shall be effective 
with respect to the unpaid principal balance of such LIBOR Amounts.

     (vi)   Borrower shall pay to Lender, on demand, such amount as Lender 
reasonably determines (determined as though 100% of the applicable LIBOR 
Amount had been funded in the London interbank market) is necessary to 
compensate Lender for any direct or indirect losses, expenses, liabilities, 
costs, expenses or reductions in yield to Lender, whether incurred in 
connection with liquidation or re-employment of funds or otherwise, incurred 
or sustained by Lender as a result of: (A) Any payment or prepayment of a 
LIBOR Amount, termination of the LIBOR Borrowing Rate or conversion of a 
LIBOR Amount to the Prime Borrowing Rate on a day other than the last day of 
the applicable LIBOR Interest Period (including as a result of acceleration 
or a notice pursuant to Section 4(c)(v)); or (B) Any failure of Borrower to 
borrow, continue or prepay any LIBOR Amount or to convert any portion of the 
Prime Rate Amount to a LIBOR Amount after Borrower has given a notice thereof 
to Lender.

     (vii)  If Borrower chooses the LIBOR Borrowing Rate, Borrower shall pay 
interest based on such rate, plus any other applicable taxes or charges 
hereunder, even though Lender may have obtained the funds loaned to Borrower 
from sources other than the London Interbank market. Lender's determination of 
the LIBOR Borrowing Rate and any such taxes or charges shall be conclusive 
in the absence of manifest error.

     (viii) Notwithstanding any other term of this note, Borrower may not 
select the LIBOR Borrowing Rate if an event of default hereunder has occurred 
and is continuing.

     (ix)   Nothing contained in this note, including without limitation the 
determination of any LIBOR Interest Period or Lender's quotation of any LIBOR 
Borrowing Rate, shall be construed to prejudice Lender's right, if any, to 
decline to make any requested Advance or to require payment on demand.

5.   COMPUTATION OF INTEREST. All interest under Section 4 and Section 11 
will be computed at the applicable rate based on a 360-day year and applied 
to the actual number of days elapsed.

6.   PAYMENT SCHEDULE.

(a)  PRINCIPAL. Principal shall be paid:

     /x/    on demand.
     / /    on demand, or if no demand, on ______.
     / /    on ______.
     / /    subject to Section 8, in installments of
            / /    _____ each, plus accrued interest, beginning on ______ 
                   and on the same day of each ______ thereafter until 
                   _______ when the entire Principal Balance plus interest 
                   thereon shall be due and payable.
            / /    _____ each, including accrued interest, beginning on ______ 
                   and on the same day of each ______ thereafter until 
                   _______ when the entire Principal Balance plus interest 
                   thereon shall be due and payable.
     / /    ______.

(b)  INTEREST.

     (i)    Interest on the Prime Rate Amount shall be paid:

            /x/    on the 1ST day of JUNE and on the same day of each MONTH. 
                   thereafter prior to maturity and at maturity.
            / /    at maturity.
            / /    at the time each principal installment is due and at 
                   maturity.
            / /    ______.

     (ii)   Interest on all LIBOR Amounts shall be paid:

            /x/    on the last day of the applicable LIBOR Interest Period, 
                   and if such LIBOR Interest Period is longer than three 
                   months, on the last day of each three month period occurring 
                   during such LIBOR Interest Period, and at maturity.
            / /    on the _____ day of _____ and on the same day of each 
                   _____ thereafter prior to maturity and at maturity.
            / /    at maturity.
            / /    at the time each principal installment is due and at 
                   maturity.
            / /    ______.

7.   PREPAYMENT.

(a)  Prepayments of all or any part of the Prime Rate Amount may be made at 
     any time without penalty.
(b)  Except as otherwise specifically set forth herein, Borrower may not 
     prepay all or any part of any LIBOR Amount or terminate any LIBOR 
     Borrowing Rate, except on the last day of the applicable LIBOR Interest 
     Period.


                                                                     Page 2 of 4

<PAGE>

(c)  Principal prepayments will not postpone the date of or change the 
     amount of any regularly scheduled payment. At the time of any principal 
     prepayment, all accrued interest, fees, costs and expenses shall also 
     be paid.

8.   CHANGE IN PAYMENT AMOUNT. Each time the interest rate on this note 
changes the holder of this note may, from time to time, in holder's sole 
discretion, increase or decrease the amount of each of the installments 
remaining unpaid at the time of such change in rate to an amount holder in 
its sole discretion deems necessary to continue amortizing the Principal 
Balance at the same rate established by the installment amounts specified in 
Section 6(a), whether or not a "balloon" payment may also be due upon 
maturity of this note. Holder shall notify the undersigned of each such 
change in writing.  Whether or not the installment amount is increased under 
this Section 8, Borrower understands that, as a result of increases in the 
rate of interest the final payment due, whether or not a "balloon" payment, 
shall include the entire Principal Balance and interest thereon then 
outstanding, and may be substantially more than the installment specified in 
Section 6.

9.   ALTERNATE PAYMENT DATE. Notwithstanding any other term of this note, if 
any month there is no day on which a scheduled payment would otherwise be due 
(e.g. February 31), such payment shall be paid on the last banking day of 
that month.

10.  PAYMENT BY AUTOMATIC DEBIT.

/ /  Borrower hereby authorizes Lender to automatically deduct the amount of 
all principal and interest payments from account number 139-0008-934 at 
WASHINGTON SQUARE. If there are insufficient funds in the account to pay the 
automatic deduction in full, Lender may allow the account to become 
overdrawn, or Lender may reverse the automatic deduction. Borrower will pay 
all the fees in the account which result from the automatic deductions, 
including any overdraft and non-sufficient funds charges. If for any reason 
Lender does not charge the account for a payment, or if an automatic payment 
is reversed, the payment is still due according to this note. If the account 
is a Money Market Account, the number of withdrawals from that account is 
limited as set out in the account agreement. Lender may cancel the automatic 
deduction at any time in its discretion.

Provided, however, if no account number is entered above, Borrower does not 
want to make payments by automatic debit.

11.  DEFAULT.

(a)  Without prejudice to any right of Lender to require payment on demand or 
to decline to make any requested Advance, each of the following shall be an 
event of default: (i) Borrower fails to make any payment when due, (ii) 
Borrower fails to perform or comply with any term, covenant or obligation in 
this note or any agreement related to this note, or in any other agreement or 
loan Borrower has with Lender, (iii) Borrower defaults under any loan, 
extension of credit, security agreement, purchase or sales agreement, or any 
other agreement, in favor of any other creditor or person that may materially 
affect any of Borrower's property or Borrower's ability to repay this note or 
perform Borrower's obligations under this note or any related documents, (iv) 
Any representation or statement made or furnished to Lender by Borrower or on 
Borrower's behalf is false or misleading in any material respect either now 
or at the time made or furnished, (v) Borrower dies, becomes insolvent, 
liquidates or dissolves, a receiver is appointed for any part of Borrower's 
property, Borrower makes an assignment for the benefit of creditors, or any 
proceeding is commenced either by Borrower or against Borrower under any 
bankruptcy or insolvency laws, (vi) Any creditor tries to take any of 
Borrower's property on or in which Lender has a lien or security interest. 
This includes a garnishment of any of Borrower's accounts with Lender, (vii) 
Any of the events described in this default section occurs with respect to 
any general partner in Borrower or any guarantor of this note, or any 
guaranty of Borrower's indebtedness to Lender ceases to be, or is asserted 
not to be, in full force and effect, (viii) There is any material adverse 
change in the financial condition or management of Borrower or Lender in good 
faith deems itself insecure with respect to the payment or performance of 
Borrower's obligations to Lender. If this note is payable on demand, the 
inclusion of specific events of default shall not prejudice Lender's right 
to require payment on demand or to decline to make any requested Advance.

(b)  Without prejudice to any right of Lender to require payment on demand, 
upon the occurrence of an event of default, Lender may declare the entire 
unpaid Principal Balance on this note and all accrued unpaid interest 
immediately due and payable, without notice. Upon default, including failure 
to pay upon final maturity, Lender, at its option, may also, if permitted 
under applicable law, increase the interest rate on this note to a rate equal 
to the Prime Borrowing Rate plus 5%. The interest rate will not exceed the 
maximum rate permitted by applicable law. In addition, if any payment of 
principal or interest is 19 or more days past due, Borrower will be charged a 
late charge of 5% of the delinquent payment.

12.  EVIDENCE OF PRINCIPAL BALANCE; PAYMENT ON DEMAND. Holder's records 
shall, at any time, be conclusive evidence of the unpaid Principal Balance 
and interest owing on this note. Notwithstanding any other provisions of 
this note, in the event holder makes Advances hereunder which result in an 
unpaid Principal Balance on this note which at any time exceeds the maximum 
amount specified in Section 2, Borrower agrees that all such Advances, with 
interest, shall be payable on demand.

13.  LINE OF CREDIT PROVISIONS. If the type of credit indicated in Section 1 
is a revolving line of credit or a non-revolving line of credit, Borrower 
agrees that Lender is under no obligation and has not committed to make any 
Advances hereunder. Each Advance hereunder shall be made at the sole option 
of the Lender.

14.  DEMAND NOTE. If this note is payable on demand, Borrower acknowledges 
and agrees that (a) Lender is entitled to demand Borrower's immediate payment 
in full of all amount owing hereunder and (b) neither anything to the 
contrary contained herein or in any other loan documents (including but not 
limited to, provisions relating to defaults, rights of cure, default rate of 
interest, installment payments, late charges, periodic review of Borrower's 
financial condition, and covenants) nor any act of Lender pursuant to any 
such provisions shall limit or impair Lender's right or ability to require 
Borrower's payment in full of all amounts owing hereunder immediately upon 
Lender's demand.

15.  REQUESTS FOR ADVANCES.

(a)  Any Advance may be made or interest rate option selected upon the 
request of Borrower (if an individual), any of the undersigned (if Borrower 
consists of more than one individual), any person or persons authorized in 
subsection (b) of this Section 15, and any person or persons otherwise 
authorized to execute and deliver promissory notes to Lender on behalf of 
Borrower.

(b)  Borrower hereby authorizes any ________ of the following individuals to 
request Advances and to select interest rate options: ________ unless Lender 
is otherwise instructed in writing.

(c)  All Advances shall be disbursed by deposit directly to Borrower's 
account number ________ at ________ branch of Lender, or by cashier's check 
issued to Borrower.

(d)  Borrower agrees that Lender shall have no obligation to verify the 
identity of any person making any request pursuant to this Section 15, and 
Borrower assumes all risks of the validity and authorization of such 
requests.  In consideration of Lender agreeing, at its sole discretion, to 
make Advances upon such requests, Borrower promises to pay holder, in 
accordance with the provisions of this note, the Principal Balance together 
with interest thereon and other sums due hereunder, although any Advances may 
have been requested by a person or persons not authorized to do so.

16.  PERIODIC VIEW.  Lender will review Borrower's credit accommodations 
periodically.  At the time of the review, Borrower will furnish Lender with 
any additional information regarding Borrower's financial condition and 
business operations that Lender requests.  This information may include but is 
not limited to, financial statements, tax returns, lists of assets and 
liabilities, agings of receivables and payables, inventory schedules, budgets 
and forecasts.  If upon review, Lender, in its sole discretion, determines 
that there has been a material adverse change in Borrower's financial 
condition, Borrower will be in default.  Upon default, Lender shall have all 
rights specified herein.

17.  NOTICES.  Any notice hereunder may be given by ordinary mail, postage 
paid and addressed to Borrower at the last known address of Borrower as shown 
on holder's records.  If Borrower consists of more than one person, 
notification of any of said persons shall be complete notification of all.

18.  ATTORNEY FEES.  Whether or not litigation or arbitration is commenced, 
Borrower promises to pay all costs of collecting overdue amounts.  Without 
limiting the foregoing, in the event that holder consults an attorney 
regarding the enforcement of any of its rights under this note or any 
document securing the same, or if this note is placed in the hands of an 
attorney for collection or if suit or litigation is brought to enforce this 
note or any document 


                                                                     Page 3 of 4

<PAGE>

securing the same, Borrower promises to pay all costs thereof including such 
additional sums as the court or arbitrator(s) may adjudge reasonable as 
attorney fees, including without limitation, costs and attorney fees 
incurred in any appellate court, in any proceeding under the bankruptcy code, 
or in any receivership and post-judgment attorney fees incurred in enforcing 
any judgment.

19.  WAIVERS; CONSENT. Each party hereto, whether maker, co-maker, guarantor 
or otherwise, waives diligence, demand, presentment for payment, notice of 
non-payment, protest and notice of protest and waives all defenses based on 
suretyship or impairment of collateral. Without notice to Borrower and 
without diminishing or affecting Lender's rights or Borrower's obligations 
hereunder, Lender may deal in any manner with any person who at any time is 
liable for, or provides any real or personal property collateral for, any 
indebtedness of Borrower to Lender, including the indebtedness evidenced by 
this note. Without limiting the foregoing, Lender may, in its sole 
discretion: (a) make secured or unsecured loans to Borrower and agree to any 
number of waivers, modifications, extensions and renewals of any length of 
such loans, including the loan evidenced by this note; (b) impair, release 
(with or without substitution of new collateral), fail to perfect a security 
interest in, fail to preserve the value of, fail to dispose of in accordance 
with applicable law, any collateral provided by any person; (c) sue, fail to 
sue, agree not to sue, release, and settle or compromise with, any person.

20.  JOINT AND SEVERAL LIABILITY. All undertakings of the undersigned 
Borrowers are joint and several and are binding upon any marital community of 
which any of the undersigned are members. Holder's rights and remedies under 
this note shall be cumulative.

21.  SEVERABILITY. If any term or provision of this note is declared by a 
court of competent jurisdiction to be illegal, invalid or unenforceable for 
any reason whatsoever, such illegality, invalidity or unenforceability shall 
not affect the balance of the terms and provisions hereof, which terms and 
provisions shall remain binding and enforceable, and this note shall be 
construed as if such illegal, invalid or unenforceable provision had not been 
contained herein.

22.  ARBITRATION. 

(a)  Either Lender or Borrower may require that all disputes, claims, 
counterclaims and defenses, including those based on or arising from any 
alleged tort ("Claims") relating in any way to this note or any transaction 
of which this note is a part (the "Loan"), be settled by binding arbitration 
in accordance with the Commercial Arbitration Rules of the American 
Arbitration Association and Title 9 of the U.S. Code. All Claims will be 
subject to the statutes of limitation applicable if they were litigated. 
This provision is void if the Loan, at the time of the proposed submission 
to arbitration, is secured by real property located outside of Oregon or 
Washington, or if the effect of the arbitration procedure (as opposed to any 
Claims of Borrower) would be to materially impair Lender's ability to realize 
on any collateral securing the Loan.

(b)  If arbitration occurs and each party's Claim is less than $100,000, one 
neutral arbitrator will decide all issues; if any party's Claim is $100,000 
or more, three neutral arbitrators will decide all issues. All arbitrators 
will be active Oregon State Bar members in good standing. All arbitration 
hearings will be held in Portland, Oregon. In addition to all other powers, 
the arbitrator(s) shall have the exclusive right to determine all issues of 
arbitrability. Judgment on any arbitration award may be entered in any court 
with jurisdiction.

(c)  If either party institutes any judicial proceeding relating to the Loan, 
such action shall not be a waiver of the right to submit any Claim to 
arbitration. In addition, each has the right before, during and after any 
arbitration to exercise any number of the following remedies, in any order or 
concurrently: (i) setoff; (ii) self-help repossession; (iii) judicial or 
non-judicial foreclosure against real or personal property collateral; and 
(iv) provisional remedies, including injunction, appointment of receiver, 
attachment, claim and delivery and replevin.

23.  GOVERNING LAW. This note shall be governed by and construed and enforced 
in accordance with the laws of the State of Oregon without regard to 
conflicts of law principles; PROVIDED, however, that to the extent that 
Lender has greater rights or remedies under Federal law, this provision shall 
not be deemed to deprive Lender of such rights and remedies as may be 
available under Federal law.

24.  DISCLOSURE. 

UNDER OREGON LAW, MOST AGREEMENTS, PROMISES AND COMMITMENTS MADE BY LENDERS 
AFTER OCTOBER 3, 1989 CONCERNING LOANS AND OTHER CREDIT EXTENSIONS WHICH ARE 
NOT FOR PERSONAL, FAMILY OR HOUSEHOLD PURPOSES OR SECURED SOLELY BY THE 
BORROWER'S RESIDENCE MUST BE IN WRITING, EXPRESS CONSIDERATION AND BE SIGNED 
BY THE LENDER TO BE ENFORCEABLE.

EACH OF THE UNDERSIGNED HEREBY ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF 
THIS DOCUMENT.


SUMMIT DESIGN, INC.
------------------------------------       ------------------------------------
Borrower Name (Corporation, Partnership    Signature of Individual Borrower
or other Entity)

/s/ C. Albert Koob          CFO
------------------------------------       ------------------------------------
By                         Title           Signature of Individual Borrower

------------------------------------       ------------------------------------
By                         Title           Signature of Individual Borrower

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


For valuable consideration, Lender agrees to the terms of the arbitration 
provision set forth in this note.

                                    Lender Name: U.S. BANK NATIONAL ASSOCIATION
                                                -------------------------------

                                    By: 
                                           ------------------------------------

                                    Title: 
                                           ------------------------------------

                                    Date: 
                                           ------------------------------------


                                                                     Page 4 of 4

<PAGE>

                              SUMMIT DESIGN, INC.
                                  "EXHIBIT A"
                     TO PROMISSORY NOTE DATED MAY 1, 1998


     Borrower's interest rate shall be tied to a Pricing Matrix based upon 
     Borrower's Debt to Tangible Net Worth Ratio.

     The Debt to Tangible Net Worth Ratio is defined as: Total Liabilities 
     minus unearned Revenue DIVIDED BY Shareholders' Equity minus Intangibles.

     The interest rate option shall be adjusted quarterly based upon the 
     following Pricing Matrix:


<TABLE>
<CAPTION>
        ----------------------------------------------------------------
          DEBT TO TANGIBLE NET WORTH   PRIME + SPREAD   LIBOR + SPREAD
                    RATIO
        ----------------------------------------------------------------
          <S>                          <C>              <C>
               GREATER THAN .50             0 bps          225 bps
                 0.26 TO 0.50               0 bps          200 bps
                LESS THAN 0.26              0 bps          150 bps
        ----------------------------------------------------------------
</TABLE>




Summit Design, Inc.

/s/ C. Albert Koob          CFO      4/30/98
---------------------------------------------
signature/title                       Date