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                 Drive Status Bytes Found in BIOS Data Area

              Drive recalibration status (at 40:3E)

                |7|6|5|4|3|2|1|0| byte at 40:3E
                 | | | | | | | +--- 1=recalibrate drive 0
                 | | | | | | +---- 1=recalibrate drive 1
                 | | | | | +----- 1=recalibrate drive 2
                 | | | | +------ 1=recalibrate drive 3
                 | +----------- unused
                 +------------ 1=working interrupt flag

              Diskette motor status

                |7|6|5|4|3|2|1|0| byte at 40:3F
                 | | | | | | | +--- 1=drive 0 motor on
                 | | | | | | +---- 1=drive 1 motor on
                 | | | | | +----- 1=drive 2 motor on
                 | | | | +------ 1=drive 3 motor on
                 | +----------- unused
                 +------------ 1=write operation

              Disk Status Byte

                |7|6|5|4|3|2|1|0| byte at 40:41
                 | | | | | | | +--- invalid diskette command
                 | | | | | | +---- diskette address mark not found
                 | | | | | +----- sector not found
                 | | | | +------ diskette DMA error
                 | | | +------- CRC check / data error
                 | | +-------- diskette controller failure
                 | +--------- seek to track failed
                 +---------- diskette time-out

              Last diskette data rate selected

                |7|6|5|4|3|2|1|0| byte at 40:8B
                 | | | | +--------- step rate time selected (see below)
                 +---------------- data rate selected (see below)

              Bits
               76  Diskette Data Rate Selected
                 00  500K bps
                 01  300K bps
                 10  250K bps
                 11  reserved

              Bits
               54  Diskette Step Rate Time Selected
                 00  step rate time of 0C
                 01  step rate time of 0D
                 10  step rate time of 0A
                 11  reserved

              Media state for fixed drives (bytes at 40:90-93)

                |7|6|5|4|3|2|1|0| bytes at 40:90-40:93
                 | | | | | +------- reserved (set to 1)
                 | | | | +-------- reserved
                 | | | +--------- 0=media/drive unestablished
                 | | +---------- reserved
                 +------------- data rate (see below)

              Bits
               76  Fixed Disk Data Rate Selected
                 00  500K bps
                 01  reserved
                 10  250K bps
                 11  reserved

        - not all OEM's implemented these bytes identically.  Some are
          also AT specific.