Date: Dec 12, 1990                           X3T9.2/90-181R1

    To: X3T9.2 Committee (SCSI)

    From: George Penokie (IBM)

    Subject: Overlapped Commands on AT bus

    There is no guidance in the ATA Rev. 2.2 standard on what
    action a drive should take if it receives a command before it
    has completed execution of an existing command.  Below are
    words which I believe should be added to the ATA standard to
    define which actions the drive should take.


    Place the following paragraphs in section 9. Command
    Descriptions just before the TABLE 9-1.


    If a new command is issued to a drive which has an
    uncompleted command (subsequently referred to as Old_Command)
    in progress, the drive shall immediately respond to the new
    command (subsequently referred to as New_Command), even if
    execution of the Old_Command could have been be completed.

    There shall be no indication given to the system as to the
    status of the Old_Command which was being executed at the
    time the New_Command was issued.