CS80 describe of /dev/rct:
  controller:   0x8003  installed unit word
                  1250  max instantaneous xfr rate (Kbytes/sec)
                     1  CS/80 integrated multi-unit controller
  unit:              2  generic device type (tape)
                079080  device number (6 bcd digits)
                  1024  # of bytes per block
                     4  # of blocks buffered
                     0  recommended burst size
                 30000  blocktime (microseconds)
                    35  continuous average transfer rate (Kbytes/sec)
                    10  optimal retry time (centiseconds)
                 24000  access time parameter (centiseconds)
                     0  maximum interleave factor
                  0x00  fixed volume byte
                  0x01  removeable volume byte
  volume:            0  maximum cylinder address
                     0  maximum head address
                     0  maximum sector address
                 65407  maximum single-vector address
                     0  current interleave factor