CS80 describe of /dev/rhd:
  controller:   0x8001  installed unit word
                  1000  max instantaneous xfr rate (Kbytes/sec)
                     1  CS/80 integrated multi-unit controller
  unit:              0  generic device type (fixed disc)
                079450  device number (6 bcd digits)
                   256  # of bytes per block
                    20  # of blocks buffered
                     0  recommended burst size
                   531  blocktime (microseconds)
                   414  continuous average transfer rate (Kbytes/sec)
                    10  optimal retry time (centiseconds)
                   500  access time parameter (centiseconds)
                     1  maximum interleave factor
                  0x01  fixed volume byte
                  0x00  removeable volume byte
  volume:          967  maximum cylinder address
                     6  maximum head address
                    31  maximum sector address
                216831  maximum single-vector address
                     1  current interleave factor