    =

    AST RESEARCH, INC.        TECHNICAL BULLETIN # 1106                3-27-95

    =

    				FLOPPY DISKETTE FORMAT COMPATIBILITY

    PROBLEM

    Attempts to format a 1.44MB as a 720KB, or a 720KB as a 1.44MB may produce an
    unstable product up to and including loss of data.

    CAUSE

    Some drives rely on an internal sensor to determine the diskette type, and
    therefore the permitted data density, and others rely on the state of a
    control line from the system floppy controller.  The Epson and Mitsumi drives
    are set to react to the sensor in the drive.  If the sensor detects the extra
    hole in the diskette jacket of a High Density diskette, it reads and writes
    only 1.44 MB format diskettes.  If it detects the absence of the hole in a
    Double Density diskette, it reads and writes only 720 KB format.  An Alps
    drive, on the other hand, does not include the internal sensor, and relies on
    the signal on pin 2 of the interface to determine the read and write density.
    On the Alps drive, you can therefore record 720 KB on a High Density diskette
    or 1.44 MB on a Double Density diskette.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    AST factory installed 3.5" floppy drives.

    SOLUTION

    A 1.44MB floppy disk should only be formatted as 1.44MB, and a 720KB diskette
    should only be formatted as a 720KB diskette.