CS80 describe of /dev/rct:
  controller:   0x8003  installed unit word
                   400  max instantaneous xfr rate (Kbytes/sec)
                     5  SS/80 integrated multi-unit controller
  unit:              0  generic device type (fixed disc)
                091531  device number (6 bcd digits)
                   256  # of bytes per block
                     1  # of blocks buffered
                     0  recommended burst size
                   690  blocktime (microseconds)
                   174  continuous average transfer rate (Kbytes/sec)
                  4500  optimal retry time (centiseconds)
                  4500  access time parameter (centiseconds)
                    27  maximum interleave factor
                  0x01  fixed volume byte
                  0x00  removeable volume byte
  volume:         1403  maximum cylinder address
                     1  maximum head address
                    27  maximum sector address
                 78623  maximum single-vector address
                     1  current interleave factor