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                                                               Exhibit 4.(a)(iv)

                      ADDENDUM TO MADGE/CELESTICA CONTRACTS

THIS ADDENDUM, effective December 21, 1999, is an addendum to the agreements
listed below and is entered into between: -

(1)   MADGE NETWORKS N.V. whose registered office is Transpolis, Schipol
      Airport, Polaris Avenue 23, 2132 JH Hoofddorp, The Netherlands;
      ("Madge") and

(2)   CELESTICA IRELAND LIMITED a limited company incorporated in Ireland whose
      registered office is at 25/28 North Wall Quay, Dublin 1 ("Celestica")

together Madge and Celestica are the "Parties".

The agreements to which this is an addendum are as follows:-

(1)   The Manufacture and Supply Agreement (as amended by letter agreement dated
      March 16, 1998) dated February 23, 1998 entered into between Madge and
      Celestica Ireland B.V. (the "Manufacturing Agreement");

(2)   The Guarantee and Indemnity dated February 23, 1998 entered into
      between Madge, Celestica and Celestica Ireland B.V. (the "Guarantee");

(3)   The Payment Agreement dated February 23, 1998 entered into, inter alia,
      between Madge and Celestica (the "Payment Agreement")

Together these 3 agreements are referred to as the "Agreements" and this
document as the "Addendum".

WHEREAS the Parties entered into the Agreements on February 23, 1998. In the
case of the Manufacturing Agreement and the Guarantee, Celestica Ireland B.V.
was also party to these agreements. By an assignment agreement dated June 17,
1998 a transfer was effected as of March 23, 1998, whereby Celestica Ireland
B.V. assigned all its rights and obligations under the Agreements (where
applicable) to Celestica;

WHEREAS Celestica has become concerned about its exposure to Madge under the
terms of the existing Agreements;

WHEREAS Madge acknowledges Celestica's concern and although Madge has no
contractual obligation to do so Madge agrees to this Addendum to attempt to
alleviate Celestica's concerns as a gesture of good faith in recognition of the
relationship between the Parties .

IN CONSIDERATION of the promises made below the Parties agree to enter into this
Addendum to amend the terms of the Agreements as follows:-


1.    EXCESS AND RESIDUAL INVENTORY:-

1.1   Madge will pay to Celestica the sum of two million US Dollars ($2m) on or
      before January 6, 2000. This is an advanced payment to Celestica based
      upon the Parties assessment of the maximum amount of monies owed by Madge
      to Celestica under the Residual and Excess Inventory provisions in the
      Manufacturing and Supply Agreement for the purchase of the Residual and
      Excess inventory. Celestica and Madge undertake that they will work
      together to define and agree, before January 21, 2000, the actual level of
      Excess and Residual Inventory, and therefore the amount due from Madge to
      Celestica as per the Manufacturing and Supply Agreement.


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1.2   In order to ensure agreement is reached under 1.1 above as soon as
      practicable any items that are still in dispute by January 20, 2000 will
      be escalated to the GM of Celestica and VP Operations of Madge.connect for
      resolution by January 21, 2000.

1.3   In the event the amount of the agreed Excess and Residual Inventory
      exceeds two million US dollars ($2m) Madge will pay Celestica the
      difference to purchase the inventory within 10 working days of the said
      agreement.

1.4   In the event the amount of agreed Excess and Residual Inventory is less
      than two million US Dollars ($2m) Madge will deduct this from the next
      scheduled recovery payment to Celestica.

1.5   In the event that Celestica needs some of the product purchased by Madge
      under this clause 1 in order to meet their obligations to Madge under the
      Manufacture and Supply Agreement Celestica will re-purchase all such
      inventory at the same prices as paid by Madge. Payment by Celestica to
      Madge will be due at the end of the month following the month of invoice.

1.6   In the event that agreement required in clause 1.1 is not reached by
      January 21, 2000 despite both parties having made all reasonable efforts
      Madge will withhold fifty percent (50%) of any disputed amounts Madge
      considers is owing to it under clause 1.4 from the next payment to
      Celestica under the Manufacturing and Supply Agreement until this matter
      is resolved.

2.    ADVANCE PAYMENT OF RECOVERIES

2.1   Assuming Celestica meets its obligations in Clause 1 above, Madge agrees
      to make cash payments in advance of the recovery schedule to Celestica of
      one million, five hundred thousand US dollars ($1.5m) on February 28, 2000
      and of one million, five hundred thousand US dollars ($1.5m) on March 31,
      2000. Both these payments are advances on the Minimum Recovery due to
      Celestica under the Guarantee.

2.2   Before May 1, 2000 Madge and Celestica will agree on the remaining level
      of the Minimum Recovery payable by Madge to Celestica under the terms of
      the Guarantee. This will then be divided into monthly payments due from
      Madge to Celestica each month for the period from May 2000 to February
      2001 as per the terms of the Guarantee.


3.    REVIEW OF CELESTICA'S EXPOSURE

3.1.  Madge and Celestica jointly undertake to formulate, agree and enact a
      series of operational initiatives to minimise Celestica's net exposure at
      any given point in time (defined for the purposes of this Addendum as
      Receivables plus Inventory on hand plus non-cancellable purchase orders,
      less the Product Discount Amount and interest thereon). The target for the
      joint team is to ensure that by March 31st, 2000 the net exposure
      Celestica currently perceives is reduced by $3.7m. Going forward from
      April 1st, 2000, Madge will use all reasonable efforts to meet targets for
      Celestica's net exposure agreed as part of the Management reviews
      described in 3.3 below.

3.2.  The actions that Madge and Celestica agree upon shall form part of the
      normal monthly operations review between Madge and Celestica.

3.3.  In addition to the operations review mentioned in 3.2 above there will be
      a separate Management review each month, initiated by Celestica, to review
      the following:

      -     Status report on Celestica's net exposure and the programme to
            maintain it at or below agreed target levels.


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      -     Update on Madge's financial strength. Madge will supply information
            to Celestica in this regard only if there is a Non Disclosure
            Agreement, acceptable to Madge in force at the time of disclosure;
            and

      -     Review of the top level operational issues between Madge and
            Celestica, focusing in particular on any areas where one party
            considers that the contractual commitments of the other party as set
            out in the Agreements or this Addendum are not being met. Such
            issues will be discussed and resolved as they arise.

      3.4 The monthly review referred to in 3.3 will be attended in person or by
      telephone by (a minimum of) the GM Celestica Ireland Limited, CFO Madge
      NV, CEO Madge.connect, VP Operations Madge.connect and the Treasurer
      Celestica Inc.

4.    MINIMUM REVENUE REQUIREMENT REMOVED

4.1   Upon receipt of payment by Madge under 2.1, Celestica agrees to delete all
      references in the Agreements to the Minimum Revenue requirement to be
      achieved by Madge. Any clauses in the Agreements which refer to the
      Minimum Revenue or the requirement that Celestica receives at least two
      hundred million US Dollars (US$200,000,000) in revenue (for example as per
      the definition of "Total Recovery Period" in the Guarantee) shall hereby
      have that wording deleted and the rest of the specific clause, as far as
      relevant, will remain in full force and effect.

5.    PAYMENT OF THE PREMIUM

5.1   Celestica will issue a certificate to Bank of Nova Scotia pursuant to
      clause 3.3 of the Payment Agreement, for payment by February 22, 2001 to
      Madge of the Product Discount Amount plus interest, provided that Madge
      has paid to Celestica the Minimum Recovery required under the terms of the
      Guarantee (as amended by this Addendum) by February 15, 2001, with no
      portion of the Product Discount Amount payable prior to this date.

5.2   This sum will be payable in one lump sum, will not be dependant upon Madge
      achieving any minimum revenue numbers nor upon Madge continuing to give
      recoveries to Celestica after this date.

5.3   The Parties agree that as part of the management review process in clause
      3.3 above when the perceived exposure is reduced and normal EMS to
      Customer trading conditions are resumed, the Parties will discuss the
      possibility of Celestica releasing the Product Discount Amount prior to
      February 28, 2001.

5.4   In the event that Madge has not met the Minimum Recovery required under
      the Agreements as of February 15, 2001 Celestica will issue a certificate
      to the Bank of Nova Scotia only for that amount of the Product Discount
      Amount plus interest that is due to Madge as determined on a pro-rata
      basis by assessment of the actual Recovery received as of February 15,
      2001 against the Minimum Recovery. The balance of the Product Discount
      Amount plus interest will revert to Celestica as originally allowed for in
      section 3.7 of the Payment Agreement.





SIGNED by the Parties and Effective the date appearing at the start of this
Addendum:-


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For and on behalf of Madge Networks NV                /s/ Michael D. Wilson
By M Wilson, CEO of Madge.connect                     ------------------------





For and on behalf of Celestica Ireland Limited        /s/ Don O'Callaghan
By D O'Callaghan, GM of Celestica Ireland Limited     ------------------------


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