    AST RESEARCH, INC.         TECHNICAL BULLETIN #0789                  11-19-92

             PREMIUM 486/25 SYSTEMS AND NOVELL NON-DEDICATED NETWARE 2.2

    PROBLEM:       After installing an Intel Overdrive processor (ODPR486DX-25)
                   into an AST Premium 486/25 system configured with Novell Non-
                   Dedicated Netware 2.2, the system will briefly display the
                   message "ABEND: Double Exception Interrupt" and then reboot
                   when attempting to start the server.

    CAUSE:         Novell Netware 2.2 uses timing dependent loops when toggling
                   the status of the GATEA20 line.  With the Intel Overdrive chip
                   installed, this loop executes so quickly that the GATEA20 line
                   is not set to the proper state before Netware begins accessing
                   extended memory.

    AFFECTED
    SYSTEMS:       AST CUPID Desktop Systems (motherboard part number 202356-00X
                   & 202337-00X).

    SOLUTION:      The file NET$OS.EXE may be patched to increase the length of
                   the timing dependent loops.  The following procedure uses the
                   DOS DEBUG command to implement this fix:

                   c:\>copy net$os.exe net$os.bin

                   debug net$os.bin
                   - s 100 FFFF 8B 0E 71 05
                   xxxx:yyyy
                   - e xxxx:yyyy
                   xxxx:yyyy  8B.B9 0E.C0 71.00 05.90
                   - s (x+1)xxx:0000 FFFF 8B 0E C8 4B
                   XXXX:YYYY
                   - e XXXX:YYYY
                   XXXX:YYYY  8B.B9 0E.C0 C8.00 4B.90
                   -w
                   Writing zzzzz bytes
                   -q

                   C:\>copy net$os.exe net$os.old
                   1 file(s) copied

                   C:\>copy net$os.bin net$os.exe
                   1 file(s) copied