Document:

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                                                                    EXHIBIT 10.6

                                ATMEL CORPORATION

                  Zero Coupon Subordinated Debentures Due 2018

                          FIRST SUPPLEMENTAL INDENTURE

                          Dated as of October 15, 1999

                                       to

                                    INDENTURE

                           Dated as of April 21, 1998

             STATE STREET BANK AND TRUST COMPANY OF CALIFORNIA, N.A.
<PAGE>
         FIRST SUPPLEMENTAL INDENTURE (the "First Supplemental Indenture") dated
as of October 15, 1999 between Atmel Corporation, a Delaware corporation ("Atmel
Delaware"), and State Street Bank and Trust Company of California, N. A.,
organized and existing under the laws of the United States (the "Trustee").

                              W I T N E S S E T H:

         WHEREAS, there has previously been executed and delivered to the
Trustee an Indenture dated as of April 21, 1998 (the "Indenture"), providing for
the issuance of Zero Coupon Convertible Subordinated Debentures due 2018 (the
"Debentures") of Atmel Corporation, a California corporation ("Atmel
California"); and

         WHEREAS, Atmel California has merged (or will merge substantially
concurrently with the execution and delivery of this First Supplemental
Indenture) with and into Atmel Delaware (the "Merger"), with Atmel Delaware as
the surviving corporation in the Merger pursuant to an Agreement and Plan of
Merger, dated as of September 17, 1999, between Atmel California and Atmel
Delaware; and

         WHEREAS, pursuant to the Merger each outstanding share of common stock
of Atmel California is converted into one outstanding share of common stock of
Atmel Delaware; and

         WHEREAS, in the case of a merger of Atmel California with and into any
other corporation, Article 5 and Section 11.14 of the Indenture require that the
surviving corporation execute and deliver to the Trustee a supplemental
indenture providing for certain conversion rights to Holders of the Securities
and the assumption by the surviving corporation of the covenants, agreements and
obligations of the Company under the Indenture; and

         WHEREAS, Section 9.01 of the Indenture provides that the Company (as
defined in the Indenture) and the Trustee may, without the consent of any
Debentureholders, enter into a supplemental indenture to comply with the terms
of Article 5 and Section 11.14 of the Indenture; and

         WHEREAS, in accordance with Sections 9.01(2), 5.01 and 12.05 of the
Indenture, the Company (as defined in the Indenture) has delivered to the
Trustee an Officers' Certificate and an Opinion of Counsel, each stating that
the Merger and the First Supplemental Indenture comply with the applicable
provisions of the Indenture; and

         WHEREAS, all acts and proceedings required by law, under the Indenture
and by the Certificate of Incorporation of Atmel Delaware to constitute this
First Supplemental Indenture a valid and binding agreement for the uses and
purposes set forth herein, in accordance with its terms, have been done and
taken, and the execution and delivery of this First Supplemental Indenture have
been in all respects duly authorized by Atmel Delaware; and
<PAGE>
         WHEREAS, the foregoing recitals are made as representations of fact by
Atmel Delaware and not by the Trustee;

         NOW, THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, Atmel
Delaware and the Trustee hereby agree as follows:

         1. For purposes of this First Supplemental Indenture, except as
otherwise herein expressly provided or unless the context otherwise requires:
(i) the capitalized terms and expressions used herein shall have the same
meanings as corresponding terms and expressions used in the Indenture; and (ii)
the words "herein," "hereof" and "hereby" and other words of similar import used
in this First Supplemental Indenture refer to this First Supplemental Indenture
as a whole and not to any particular section hereof.

         2. Atmel Delaware hereby assumes all the covenants, agreements and
obligations of the Company under the Debentures and the Indenture, including the
obligation to make due and punctual payment of the principal of and premium, if
any, and original issue discount and interest, if any, on all of the Debentures
and the due and punctual performance of all of the covenants and conditions to
be performed by the Company under the Indenture. From and after the effective
time of the Merger, the Debentures shall be convertible into shares of common
stock of Atmel Delaware on the same terms and basis (and subject to the same
adjustments under the Indenture) as the Debentures were convertible into common
stock of Atmel California prior to the effectiveness of the Merger, and on and
after the effective time of the Merger references in the Indenture to "Common
Stock" shall be deemed to be references to common stock of Atmel Delaware.

                                                                             -2-
<PAGE>
         3. The Trustee accepts the amendment of the Indenture effected by this
First Supplemental Indenture and agrees to execute the trust created by the
Indenture, as hereby amended, including the terms and conditions as set forth in
the Indenture, as hereby amended, including the terms and provisions defining
and limiting the liabilities and responsibilities of the Trustee, which terms
and provisions shall in like manner define and limit its liabilities in the
performance of the trust created by the Indenture, as hereby amended, and
without limiting the generality of the foregoing, the Trustee has no
responsibility for the correctness of the recitals of fact herein contained
which shall be taken as the statements of Atmel Delaware and makes no
representations as to the validity or sufficiency of this First Supplemental
Indenture and shall incur no liability or responsibility in respect of the
validity thereof.

         4. Except as expressly amended hereby, the Indenture is in all respects
ratified and confirmed, and all the terms, conditions and provisions hereof
shall remain in full force and effect.

         5. This First Supplemental Indenture shall form a part of the Indenture
for all purposes, and every holder of Securities heretofore or hereafter
authenticated shall be bound hereby.

         6. This First Supplemental Indenture may be executed in any number of
counterparts, each of which when so executed shall be deemed to be an original,
and all of such counterparts shall together constitute one and the same
instrument.

         7. This First Supplemental Indenture shall be deemed to be a contract
made under the laws of the State of New York, and for all purposes shall be
governed by the construed in accordance with such laws.

                                                                             -3-
<PAGE>
         IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed, and their respective seals to be
hereunto affixed and attested, all as of the day and year first above written.

                           ATMEL CORPORATION
                           a Delaware Corporation,

                           By: /s/ George Perlegos
                               -------------------------------------------------
                                George Perlegos
                                Chairman of the Board, President and Chief
                                Executive Officer of Atmel California and Atmel
                                Delaware

                           By:   /s/ Donald Colvin
                              --------------------------------------------------
                                Donald Colvin, Vice President, Finance and Chief
                                Financial Officer of Atmel California and Atmel
                                Delaware

                           STATE STREET BANK AND TRUST
                           COMPANY, OF CALIFORNIA, N. A., as Trustee

                           By: /s/ Paula Oswald
                               -------------------------------------------------
                           Name: Paula Oswald
                           Title: Vice President

                                                                             -4-<PAGE>

                                                                     EXHIBIT 4.4

                            HORSESHOE HAMMOND, INC.,
                             AN INDIANA CORPORATION

                       INTERCOMPANY NOTE DUE MAY 15, 2009

Principal Amount: see Schedule A                              New York, New York
                                                                December 1, 1999

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        FOR VALUE RECEIVED, Horseshoe Hammond, Inc. (the "Company"), an Indiana
corporation with its principal place of business located at 777 Casino Center
Drive, Hammond, Indiana 46320, hereby promises to pay to Horseshoe Gaming
Holding Corp., a Delaware corporation and successor to Horseshoe Gaming, L.L.C.,
a Delaware limited liability company (the "Payee"), with its principal place of
business located at 18454 S. West Creek Drive, Tinley Park, Illinois 60477, or
its registered assigns, the aggregate principal amount outstanding on this Note,
from time to time, as set forth on Schedule A hereto, and to pay interest
thereon, as provided herein. Certain capitalized terms used in this Note are
defined in Section 9 below.

        1. PAYMENTS OF INTEREST. Interest (computed on the basis of a 360-day
year of twelve 30 day months) on any unpaid principal amount shall be payable at
the rate per annum set forth on Schedule A in respect of each principal amount
contributed by the Payee to the Company as set forth on Schedule A (a "Principal
Amount") from the date of contribution of such Principal Amount as set forth on
Schedule A (a "Principal Contribution Date"), payable semi-annually in arrears
on each May 15 and November 15 of each year, commencing on May 15, 2000, until
said Principal Amount shall have become due and payable.

        2. PAYMENTS OF PRINCIPAL.

        2.1 OPTIONAL REDEMPTION. This Note may be redeemed, in whole or in part,
at any time or from time to time, at the option of the Company at 100% of the
outstanding principal amount hereof, together with interest accrued thereon to
the date fixed for such optional redemption, without premium or penalty. Upon
receipt of any redemption payment, the Payee shall make a notation on this Note
of such payment received and shall provide the Company with evidence acceptable
to the Company that the payment has been received by the Payee and so noted.

        2.2 PAYMENT OF PRINCIPAL. The remaining outstanding principal balance of
this Note plus all interest accrued thereon is due in full on May 15, 2009.

        2.3 BORROWINGS. Each Principal Amount, Principal Contribution Date, the
interest rate with respect to such Principal Amount and the amount of each
payment or prepayment made on account of any such Principal Amount shall be
recorded by the Company on its books and on Schedule A attached hereto.

<PAGE>

        3. SUBORDINATION. The payment of the principal of and interest on this
Note is expressly subordinated in right of payment to the prior payment in full
of all amounts payable on, under or in connection with the indebtedness issued
pursuant to the Senior Credit Agreement and the Indenture. Upon the acceleration
of the indebtedness issued pursuant to the Senior Credit Agreement or the
Indenture following the occurrence of an Event of Default (as such term is
defined in each of the Senior Credit Agreement and the Indenture), no payments
of any kind shall be made with respect to the principal and interest of this
Note until (a) such Event of Default has been cured, waived or shall have
otherwise ceased to exist, (b) the indebtedness under the Senior Credit
Agreement or the Indenture, as applicable, shall have been discharged or paid in
full or (c) the appropriate representatives of the lenders under the Senior
Credit Agreement or the trustee or noteholders under the Indenture, as
applicable, pursuant to the terms thereof shall have consented to the making of
such payments by the Company.

        4. TRANSFER OF NOTE. This Note may not be sold, transferred, pledged or
hypothecated; provided, that this Note may be transferred to a successor of the
Company.

        5. EVENTS OF DEFAULT; REMEDIES.

        5.1 EVENTS OF DEFAULT DEFINED; ACCELERATION OF MATURITY. If any of the
following events ("Events of Default") shall occur and be continuing (for any
reason whatsoever and whether it shall be voluntary or involuntary or by
operation of law or otherwise):

        a. default shall be made in the payment of the principal of this Note
when and as the same shall become due and payable, whether at stated maturity,
by acceleration or otherwise;

        b. default shall be made in the payment of any interest on this Note
when and as such interest shall become due and payable, and such default shall
have continued for a period of thirty (30) days; or

        c. an "Event of Default," as defined in either the Senior Credit
Agreement or the Indenture, shall have occurred and be continuing;

then upon the occurrence of any Event of Default, the Payee, by written notice
to the Company, may declare the unpaid principal amount of this Note to be, and
the same shall forthwith become, due and payable, together with the interest
accrued thereon and all other amounts payable by the Company hereunder.

        The provisions of this Section are subject, however, to the condition
that if, at any time after this Note shall have so become due and payable, the
Company shall pay all arrears of interest on this Note and all payments on
account of the principal on this Note and any other amounts owing which shall
have become due otherwise than by acceleration (with interest on such principal,
and, to the extent permitted by law, on overdue payments of interest, at the
rate or rates specified in this Note) and all Events of Default (other than
nonpayment of principal of and accrued interest on this Note, due and payable
solely by virtue of acceleration) shall be remedied or waived pursuant to
Section 6, then, and in every such case, the Payee, by written notice to the
Company, may rescind and annul any such acceleration and its consequences; but
no such action shall affect any subsequent Event of Default or impair any right
consequent thereon.

                                       2
<PAGE>

        6. AMENDMENT AND WAIVER. Any term, covenant, agreement or condition of
this Note, with the consent of the Company, may be amended, or compliance
therewith may be waived (either generally or in a particular instance and either
retroactively or prospectively), by a written instrument signed by the Payee;
provided, however, that no such waiver shall extend to or affect any obligation
not expressly waived or impair any right consequent thereon.

        7. NOTICES. All notices and other communications provided for in this
Note shall be in writing and delivered, telecopied or mailed, first class
postage prepaid, addressed:

        a. if to the Company:

                             HORSESHOE HAMMOND, INC.
                             777 CASINO CENTER DRIVE
                             HAMMOND, INDIANA 46320

                             ATTENTION: CHIEF FINANCIAL OFFICER

        b. if to the Payee, at the address set forth on the first page of this
Note or at such other address as the Payee may hereafter designate by notice to
the Company.

        Any such notice or communication shall be deemed to have been duly given
when delivered or telecopied and, if mailed, two days after deposit in the U.S.
mail.

        8. REMEDIES CUMULATIVE. No remedy herein conferred upon the Payee is
intended to be exclusive of any other remedy and each and every such remedy
shall be cumulative and shall be in addition to every other remedy given
hereunder or now or hereafter existing at law or in equity or by statute or
otherwise.

        9. DEFINITIONS. Except as otherwise specified or as the context may
otherwise require, the following terms shall have the respective meanings set
forth below when used in this Note:

        "Business Day" means each Monday, Tuesday, Wednesday, Thursday and
Friday that is not a day on which banking institutions in New York, New York are
authorized or obligated by law or executive order to close.

        "Indenture" means the Indenture, dated as of May 11, 1999 and as
amended, by and between the Payee and U.S. Trust Company, National Association.

        "Senior Credit Agreement" means the Credit Agreement, dated as of June
30, 1999 and as amended, among the Payee, DLJ Capital Funding, Inc., as
Syndication Agent, Canadian Imperial Bank of Commerce, as Administrative Agent,
Wells Fargo Bank, National Association, as Documentation Agent, and the Lenders
listed therein.

        10. GOVERNING LAW. This Note shall be governed by and construed in
accordance with the internal laws of the State of New York.

                                       3
<PAGE>

        11. SEVERABILITY. If any provision of this Note shall be held to be
invalid, illegal or unenforceable in any respect, such invalidity, illegality or
unenforceability shall not affect any of the provisions hereof and this Note
shall be construed as if such invalid, illegal or unenforceable provisions had
never been contained herein.

        12. MISCELLANEOUS.

        a. Payments of all amounts owing under this Note are to be made at the
address of the Payee stated on the first page of this Note or at such other
address as the Payee may designate from time to time in writing. Any payment
date occurring on any day other than a Business Day shall be deemed to be the
next succeeding Business Day.

        b. The Company promises to pay all costs and expenses, including
reasonable attorneys' fees, incurred in the collection and enforcement of this
Note. The Company hereby consents to renewals and extensions of time at or after
the maturity hereof, without notice, and hereby waives diligence, presentment,
protest, demand and notice of every kind and, to the full extent permitted by
law, the right to plead any statute of limitations as a defense to any demand
hereunder.

                                     HORSESHOE HAMMOND, INC.,
                                     an Indiana Corporation

                                     By: /s/ Kirk C. Saylor
                                         ---------------------------------------
                                         Name:  Kirk C. Saylor
                                         Title: Chief Financial Officer

                                       4
<PAGE>

                                   SCHEDULE A

                                   Borrowings

<TABLE>
<CAPTION>
                                              Rate
    Principal              Principal           of         Amount Paid      Unpaid Principal
Contribution Date           Amount          Interest       or Prepaid            Amount
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<S>                     <C>                 <C>          <C>               <C>
December 01, 1999       $370,371,743.67      8.625%                  0      $370,371,743.67
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December 31, 2000                            8.625%      $9,548,628.33      $360,823,115.34
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</TABLE>

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