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    AST RESEARCH, INC.          TECHNICAL BULLETIN # 1251               7-14-95

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    SCO UNIX 3.2V4.2 DOES NOT USE FULL CAPACITY OF 700MB TOSHIBA DRIVE IN
    ASCENTIA 910N

    PROBLEM

    When installing SCO UNIX 3.2 V4.2 on an Ascentia 910N system with a 700MB
    TOSHIBA drive, the size of the drive is rounded down to 500MB.

    CAUSE

    SCO Unix does not support Logical Block Addressing (LBA).  When drive
    parameters appear to exceed a cylinder count of 1024, or a head count of 16 at
    boot time, SCO assumes Enhanced IDE mode (EIDE) and restricts the drive to
    a maximum size of approximately 500MB.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    All Ascentia 910N systems w/700MB Toshiba hard drives.

    SOLUTION

    The drive can be placed in an IDE-compatible mode which is supported by this
    version of SCO UNIX.  This is done by selecting "Fully Configuration
    Installation" during the install process and inputting the actual drive
    parameters from Toshiba as follows:

    Cylinders = 1365
    Heads = 16
    Sectors/track = 63
     Landing Zone = 1365
    Write Precomp = 0

    These parameters will configure the drive to 700MB.  SCO supports up to
    2048 cylinders in an IDE-compatible mode, which means that the drive can be
    up to approximately 1GB.  In normal operation, when the system is booted,
    SCO will reference the masterboot block to get the actual drive parameters.