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    AST RESEARCH, INC.        TECHNICAL BULLETIN # 1095                  3-9-95

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    				 INCOMPATIBILITY ON LARGE IDE DRIVES

    PROBLEM

    There is a potential for incompatibility on IDE drives larger than 528M, when
    switching drives from one vendor's machine to another.

    The underlying reason for this incompatibility is due to a lack of standards
    when developing a BIOS.  Various BIOS writers at different companies have
    implemented the necessary translation of the drive geometry for these larger
    drives.

    CAUSE

    The main trigger for this incompatibility is if the large drive being used
    does not specify its drive geometry to use the maximum of 63 sectors per track.
    Most drive vendors have made their large capacity drives with the 63 sector
    per track maximum.  However, there are a few models such as the Quantum LPS
    and Quantum Lightning hard drives which do not abide by this rule.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    All AST systems using IDE drives larger than 528 MB.

    SOLUTION

    Before moving a large IDE drive from one system to another, go through the
    following checklist:

    1. Do both the source and destination systems use the same BIOS vendor?
       If the answer is yes, there should not be a problem transferring any drive
       from one system to the other.

    2. If the BIOS vendor is not the same on both the source and destination
       systems, check the drive geometry.  If the sectors per track are 63,
       transfering the drive should not cause a problem. Go into System Setup and
       look under "hard drive" to find out how many sectors per track your hard
       drive has.

    3. If the BIOS vendor is not the same and, if the sectors per track of the
       drive in question are not 63, then use the user-defined drive option to
       configure the destination system with the translated drive geometry
       identified by the source system.

    Note: Back up the data before moving the drive.  If the destination and source
    systems do not use the same BIOS, the user-defined option should be used.
    In that case, the drive may not map out to the full capacity unless it is
    backed up, repartitioned, reformatted under the new user defined option.
    Simply to plug in the drive and set up user defined option will result in
    loss of some capacity (sometimes as large as 50MB.-E.M>).