    AST RESEARCH, INC.         TECHNICAL BULLETIN #0773                  08-25-92

                         3COM COMPATIBILITY IN AST EISA SYSTEMS

    PROBLEM:       There is a bus timing problem with 3COM's 3C507 Coax board
                   previous to modification 11, revision B and on the 3C507 TP
                   board modification 4, revision B.

    CAUSE:         When 3COM 3C507 Coax and 3C507 TP network interface cards are
                   installed in AST EISA based systems, the following symptoms
                   will occur:

                   - Intermittent lock ups
                   - Unreliable performance
                   - ABEND (NetWare)
                   - Trap Errors (OS/2)

    SYSTEMS
    AFFECTED:      386 Tower EISA, 486 Tower EISA, Premium SE, Power Premium, and
                   486 Desktop EISA.

    SOLUTION:      The following revisions must be installed to fix the problem:

                   The 3C507 Coax board must be a modification 11 or higher and
                   of revision B or higher.  This information is located in the
                   upper right hand column of the board and is displayed as
                   follows:

                   ASSY 6750-11 REV B

                   The 3C507 TP board must be a modification 04 or higher and of
                   revision B or higher.  This information is located in the
                   upper right hand column of the board and is displayed as
                   follows:

                   ASSY 7508-04 REV B

                   Customers with the above problem should call 3COM's RMA
                   department for an upgrade at (800) 876-3266.