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    AST RESEARCH, INC.         TECHNICAL BULLETIN # 1200A                2-8-96

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    	       Premmia GX Poor PCICLK Signal Quality On Riser Card

    PROBLEM

    The Premmia GX system may hang when executing code which involves IDE
    disk access.  Hard disk file corruption may occur in conjunction with the
    system hanging.  The failure occurs when the IDE hard drive is using the
    CMD PCI0640B IDE controller located on the system riser card
    (part number 202717-001).

    The failure occurs within the following configuration:

    1. The system is a Premmia GX P90 or P100.
    2. A PCI add-in card is in the lower slot (J1).
    3. The CMD IDE performance enhancement feature referred to as "32-bit
       disk access" has been enabled.  It is enabled using the AST utility
       SETIDE.EXE.

    The failure will never occur when the lower slot is empty.

    CAUSE

    Installation of a PCI add-in card in the lower slot causes a marked ringing on
    the PCI clock to the CMD PCI0640B IDE controller on the riser card.
    This causes an illegal clock transition at the controller which leads to
    double-clocking within the controller.  The clock signal is fine when the slot
    is empty.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    501457-XXX      PREMMIA GX P/90
    501700-XXX      PREMMIA GX P/90
    501522-XXX      PREMMIA GX P/100

    SOLUTION

    A newer version of the riser card (P/N 202717-002) for the Premmia GX
    includes a PCI clock routing modification, which does not exhibit the
    symptoms discussed under CAUSE above.  The new riser card can be
    substituted for the 202717-001 riser card in Premmia GX systems, but there
    are functional differences between the two riser cards.

    This riser card uses the CMD PCI0646 controller, which will enable
    the system to support up to two PIO mode 4 hard drives.  The PCI0640B on
    the 202717-001 supports up to two PIO mode 3 drives.

    CAUTION

    This modification should be performed only by a qualified service technician.
    It is strongly recommended that this change be completed by an AST
    Authorized Service Center.  In no case will AST Research, Inc. be liable for
    damage to the system and its components, or loss of data caused by improper
    modification.

    PREREQUISITES

    A full backup of all data on the hard drive in the computer is strongly
    suggested.

    TIME REQUIRED

    30 minutes.

    STATUS VERIFICATION

    The revision level of the AST riser card can be identified by observing the
    revision letter at the end of the nine-digit part number located on the solder
    side of the card.

    TOOLS REQUIRED

    Standard computer tools.

    INSTALLATION PROCEDURE

    Refer to the system Hardware Maintenance Manual (P/N 002143-001A).

    Removal and replacement of system "Field Replaceable Units" (FRUs)
    should only be performed according to the installation procedures approved
    and prescribed by AST Research, Inc.

    Remove the riser card according to procedures approved and prescribed by
    AST Research, Inc.

    CHECK-OUT PROCEDURE

    To verify proper operation of the system upon completion of this change,
    follow the Set-up and test procedures described in the AST User's Manual.

    NOTE

    Warranty reimbursement for this change requires prior AST Research, Inc.
    approval.

    The warranty on this system will become VOID if this change is completed
    by ANYONE other than an AST Authorized Service Center.