<PAGE>   1
                                                                    Exhibit 10.8

         THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
         SECURITIES EXCHANGE ACT OF 1933, AS AMENDED (THE "ACT") OR ANY STATE
         SECURITIES LAW AND MAY NOT BE OFFERED, SOLD, OR OTHERWISE TRANSFERRED,
         PLEDGED, OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT AND
         APPLICABLE STATE SECURITIES LAWS OR, IN THE OPINION OF COUNSEL IN FORM
         AND SUBSTANCE SATISFACTORY TO THE ISSUER OF THE SECURITIES REPRESENTED
         HEREBY, SUCH OFFER, SALE, TRANSFER, PLEDGE, OR HYPOTHECATION IS IN
         COMPLIANCE THEREWITH.

                              AMENDED and RESTATED
                                 PROMISSORY NOTE

                                                            Phoenix, Arizona
$3,100,000.00                                               as of August 1, 2001

1.    FUNDAMENTAL PROVISIONS.

      The following terms will be used as defined terms in this Promissory Note
      (as it may be amended, modified, extended and renewed from time to time,
      the "Note"):

<TABLE>
<CAPTION>
<S>                                 <C>
     Payee and Holder:              GEORGE WALLNER, a man.

     Maker:                         HYPERCOM CORPORATION, a Delaware corporation.

     Principal Amount:              Three Million One Hundred Thousand and No/100 Dollars
                                    ($3,100,000.00).

     Interest Rate:                 Twelve percent (12%) per annum.

     Default
     Interest Rate:                 Three percent (3%) per annum above the Interest Rate.

     Maturity Date:                 The earlier to occur of (i) eighteen (18) months after August
                                    1, 2001 or (ii) the first Business Day following satisfaction,
                                    in full, of all amounts outstanding under that certain Loan and
                                    Security Agreement, dated as of July 31, 2001, by and among
                                    Hypercom Corporation and certain subsidiaries thereof, Lenders
                                    signatory thereto and Foothills Capital Corporation (the "Loan
                                    Agreement").

     Business Day:                  Any day of the year other than Saturdays, Sundays and legal
                                    holidays on which Holder's main office at Bank One Arizona,
                                    N.A., is closed.

     Loan:                          The loan from Holder to Maker in the Principal Amount and
                                    evidenced by this Note.
</TABLE>
<PAGE>   2
2.    PROMISE TO PAY.

      For value received, Maker promises to pay to the order of Holder, at his
      address in Miami, Florida, or at such other place as the Holder hereof may
      from time to time designate in writing, the Principal Amount, together
      with accrued interest from the date of disbursement on the unpaid
      principal balance at the Interest Rate.

3.    INTEREST; PAYMENTS.

      (a)   Absent an Event of Default hereunder, each advance made hereunder
            shall bear interest at the Interest Rate. Throughout the term of
            this Note, interest shall be computed by applying the ratio of the
            annual interest rate over a year of 360 days, multiplied by the
            outstanding principal balance, multiplied by the actual number of
            days the principal balance is outstanding.

      (b)   Subject to the terms of that certain Subordination Agreement, dated
            as of [July 31, 2001], by and between George Wallner and Foothills
            Capital Corporation, as Agent, all payments of principal and
            interest due hereunder shall be made (i) without deduction of any
            present and future taxes, levies, imposts, deductions, charges or
            withholdings, which amounts shall be paid by Maker, and (ii) without
            any other set off. Maker will pay the amounts necessary such that
            the gross amount of the principal and interest received by the
            holder hereof is not less than that required by this Note.

      (c)   Maker shall make all payments of principal and interest due
            hereunder, and any other amounts due hereunder due and payable, on
            the Maturity Date. If any payment of principal and interest to be
            made by Maker hereunder shall become due on a day which is not a
            Business Day, such payment shall be made on the next succeeding
            Business Day and such extension of time shall be included in
            computing the interest in such payment.

4.    PREPAYMENT.

      Maker may prepay the Loan, in whole or in part, at any time without
      penalty or premium.

5.    LAWFUL MONEY.

      Principal and interest are payable in lawful money of the United States of
      America.

6.    APPLICATION OF PAYMENTS/LATE CHARGE/DEFAULT INTEREST.

      (a)   Absent the occurrence of an Event of Default hereunder, any payments
            received by the holder hereof pursuant to the terms hereof shall be
            applied to sums, other than principal and interest, due the holder
            hereof pursuant to this Note, next to the payment of all interest
            accrued to the date of such payment, and the balance, if any, to the
            payment of principal. Any payments received by the holder hereof
            after the

                                      -2-
<PAGE>   3
            occurrence of an Event of Default hereunder shall be applied to the
            amounts specified in this Paragraph 6(a) in such order as the holder
            hereof may, in its sole discretion, elect.

      (b)   If any payment of interest and/or principal is not received by the
            holder hereof when such payment is due, then in addition to the
            remedies conferred upon the holder hereof pursuant to Paragraph 9
            hereof, the amount due and unpaid shall bear interest at the Default
            Interest Rate, computed from the date on which the amount was due
            and payable until paid.

7.    EVENT OF DEFAULT.

      The (i) default in the payment of principal or interest when due pursuant
      to the terms of this Note and (ii) any default under any other material
      loan agreement executed by Maker shall be deemed to be an event of default
      ("Event of Default") hereunder.

8.    REMEDIES.

      Upon the occurrence of an Event of Default, then at the option of the
      holder hereof, the entire balance of principal together with all accrued
      interest thereon, and all other amounts payable by Maker hereunder shall,
      without demand or notice, immediately become due and payable. Upon the
      occurrence of and Event of Default (and so long as such Event of Default
      shall continue), the entire balance of principal hereof, together with all
      accrued interest thereon, and any judgment for such principal, interest,
      and other amounts shall bear interest at the Default Interest Rate,
      subject to the limitations contained in Paragraph 13 hereof. No delay or
      omission on the part of the holder hereof in exercising any right under
      this Note hereof shall operate as a waiver of such right.

9.    WAIVER.

      Maker, endorsers, guarantors, and sureties of this Note hereby waive
      diligence, demand for payment, presentment for payment, protest, notice of
      nonpayment, notice of protest, notice of intent to accelerate, notice of
      acceleration, notice of dishonor, and notice of nonpayment, and all other
      notices or demands of any kind and expressly agree that, without in any
      way affecting the liability of Maker, endorsers, guarantors, or sureties,
      the holder hereof may extend any maturity date or the time for payment of
      any installment due hereunder, accept additional security, release any
      Person liable, and release any security or guaranty. Maker, endorsers,
      guarantors, and sureties waive, to the full extent permitted by law, the
      right to plead any and all statutes of limitations as a defense.

                                      -3-
<PAGE>   4
10.   CHANGE, DISCHARGE, TERMINATION, OR WAIVER.

      No provision of this Note may be changed, discharged, terminated, or
      waived except in a writing signed by the party against whom enforcement of
      the change, discharge, termination, or waiver is sought. No failure on the
      part of the holder hereof to exercise and no delay by the holder hereof in
      exercising any right or remedy under this Note or under the law shall
      operate as a waiver thereof.

11.   ATTORNEYS' FEES.

      If this Note is not paid when due or if any Event of Default occurs, Maker
      promises to pay all costs of enforcement and collection and preparation
      therefor, including but not limited to, reasonable attorneys' fees,
      whether or not any action or proceeding is brought to enforce the
      provisions hereof (including, without limitation, all such costs incurred
      in connection with any bankruptcy, receivership, or other court
      proceedings whether at the trial or appellate level).

12.   SEVERABILITY.

      If any provision of this Note is unenforceable, the enforceability of the
      other provisions shall not be affected and they shall remain in full force
      and effect.

13.   INTEREST RATE LIMITATIONS.

      Maker hereby agrees to pay an effective rate of interest that is the sum
      of the interest rate provided for herein, together with any additional
      rate of interest resulting from any other charges of interest or in the
      nature of interest paid or to be paid in connection with the Loan. Holder
      and Maker agree that none of the terms and provisions contained herein
      shall be construed to create a contract for the use, forbearance or
      detention of money requiring payment of interest at a rate in excess of
      the maximum interest rate permitted to be charged by the laws of the State
      of Arizona. In such event, if any holder of this Note shall collect monies
      which are deemed to constitute interest which would otherwise increase the
      effective rate on this Note to a rate in excess of the maximum rate
      permitted to be charged by the laws of the State of Arizona, all such sums
      deemed to constitute interest in excess of such maximum rate shall, at the
      option of the holder, be credited to the payment of other amounts payable
      hereunder or returned to Maker.

14.   NUMBER AND GENDER.

      In this Note the singular shall include the plural and the masculine shall
      include the feminine and neuter gender, and vice versa.

15.   HEADINGS.

      Headings at the beginning of each numbered section of this Note are
      intended solely for convenience and are not part of this Note.

                                      -4-
<PAGE>   5
16.   CHOICES OF LAW.

      THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
      OF THE STATE OF ARIZONA WITHOUT GIVING EFFECT TO CONFLICT OF LAWS
      PRINCIPLES.

17.   INTEGRATION.

      This Note contains the complete understanding and agreement of the holder
      hereof and Maker and supersede all prior representations, warranties,
      agreements, arrangements, understandings and negotiations.

18.   BINDING EFFECT.

      This Note will be binding upon, and inure to the benefit of, the holder
      hereof, Maker, and their respective successors and assigns. Maker may not
      delegate its obligations under this Note.

19.   TIME OF THE ESSENCE.

      Time is of the essence with regard to each provision hereof as to which
      time is faster.

20.   SURVIVAL.

      The representations, warranties, and covenants of the Maker of this Note
      shall survive the execution and delivery of this Note and the making of
      the Loan.

21.   SUBORDINATION.

      Holder's rights to payment under this Note shall be at all times and in
      all respects wholly subordinate and inferior in claim and right to the
      obligations of Maker pursuant to the terms of the Loan Agreement. The
      terms of such subordination are set forth in that certain Wallner
      Subordination Agreement dated July 31, 2001, by and between Holder and
      Foothill Capital Corporation.

                                      HYPERCOM CORPORATION, a Delaware
                                      corporation



                                      By: /s/ Jonathon Killmer
                                          ___________________________________
                                      Name: Jonathon E. Killmer
                                      Title: Executive Vice President, Chief
                                      Financial Officer, Chief Operating
                                      Officer, Chief Administrative Officer and
                                      Secretary
                                      "MAKER"


                                      -5-