    AST RESEARCH, INC.         TECHNICAL BULLETIN #0654                  12-21-90

                         PREMIUM 386/16 WITH MATH CO-PROCESSOR

    Erratic operation may occur when using a math co-processor in the Premium
    386/16.  This condition was first observed when running AutoCAD Release 9 and
    10.  The system may lock up when running software that uses the math co-
    processor after the system has warmed up (anywhere from immediately to 30
    minutes).  The failure is encountered consistently after re-booting until the
    system has been shut off and allowed to cool down.

    The cause of the problem is a contention with the 87BUSY* signal from the
    math co-processor.  The contention situation is eliminated by lifting or
    cutting pin 16 on the chip at location U34 on the Premium 386/16 processor
    board (AST Part Number 202323-001).  Denoted after the part number is a
    revision letter (i.e., 202323-001C).  Use the following list to determine the
    appropriate action to be taken:

    Revision                      Action

    C or earlier        You should return the board to AST for modification.

    D                   Modification may be performed by an AST Authorized
                        Service Center.

    E or later          Modification has already been implemented, and no action
                        is required.

    WARNING: This operation is meant to be performed on Premium 386/16 processor
             boards only (AST Part Number 202323-001), NOT on Premium 386SX/16 or
             386SX/20 processor boards.  All modifications should be performed by
             an AST Authorized Service Center.