CS80 describe of /dev/r76:
  controller:   0x8001  installed unit word
                  1000  max instantaneous xfr rate (Kbytes/sec)
                     0  CS/80 integrated single unit controller
  unit:              0  generic device type (fixed disc)
                079580  device number (6 bcd digits)
                   256  # of bytes per block
                    64  # of blocks buffered
                     0  recommended burst size
                   265  blocktime (microseconds)
                   900  continuous average transfer rate (Kbytes/sec)
                    80  optimal retry time (centiseconds)
                   500  access time parameter (centiseconds)
                     1  maximum interleave factor
                  0x01  fixed volume byte
                  0x00  removeable volume byte
  volume:         1012  maximum cylinder address
                     7  maximum head address
                    62  maximum sector address
                510551  maximum single-vector address
                     1  current interleave factor