Xenix and Irwin Minicartridge Tape

[Doug Toppin X2075]

We are running SCO Xenix 2.2.3 on the 286 with an Irwin 2080?
minicartridge tape drive (works off of floppy controller).
We have been unable to prevent the tape from rewinding
after tar'ing to it (and using the /dev/nrctmini device).
We are also unable to append with 'tar' to a tape.
The tape always rewinds and writes to the beginning.
My questions are:

* Has anyone with our configuration been successful in appending
  to a tape?
* What are these devices used for? We have been unable to find any
  documentation referencing them.
    /dev/mc/mcdaemon
    /dev/mc/rmc0
    /dev/mc/rmc0a
    /dev/mc/rmc0nr
    /dev/mc/rmc0p

Any answers or comments are very welcome.
thanks
Doug Toppin
uunet!melpar!toppin