=============================================================================

AST RESEARCH, INC.        FIELD CHANGE NOTICE #0068A                 07-29-92

=============================================================================


                AST PREMIUM II 486SX/20 CPU OVERDRIVE UPGRADE


PURPOSE:            To provide a resolution to a POST 1 error (the 1st 64kb
                    memory test) when adding a P23T processor upgrade
                    (overdrive) to the co-processor socket on the discreet
                    CPU card, part number 202436-XXX.  The PAL chip at
                    location U54 should be exchanged for a new PAL, part
                    number 238125-002.  The ASIC, part number 202439-XXX, and
                    ASIC PQFP, part number 202439-xxx, CPU cards display this
                    error and a fix has been implemented.  This was
                    accomplished by changing the value of resistors R21 and
                    R22.  However, the R21 & R22 resisistors cannot be
                    replaced at the field level.  The entire 202439 CPU card
                    should be treated as an FRU.

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

PREREQUISITES:      None

TIME REQUIRED:      30 Minutes

ASSEMBLIES
AFFECTED:               AST                                REVISION
                    PART NUMBER       DESCRIPTION            LEVEL

                    202436-XXX        Processor Card         All


STATUS
VERIFICATION:       Observe location U54 part number for the new PAL chip.

PARTS
REQUIRED:                       AST
                    QTY      PART NUMBER     REVISION   DESCRIPTION

                     1       238125-002         A       PAL Chip

TOOLS
REQUIRED:           Standard computer tools

DIAGNOSTICS
REQUIRED:           None

INSTALLATION
PROCEDURE:          Removal and replacement of system "Field Replaceable
                    Units" (F.R.U.s) should only be performed according to
                    the installation procedures approved and prescribed by
                    AST Research, Inc.

CHECK-OUT
PROCEDURE:          To verify proper operation of the system upon completion
                    of this FCN, follow the setup and test procedures
                    described in the AST User's Manual.