problems with cpio

[Monty BSD]

we've been having a problem with cpio and our tape drive.  when we run
cpio with the -B option (5120 blocksize), we get the messages:

	vmunix: xt0: lost interrupt
	vmunix: xt0: bad command synchronization

and cpio aborts.  its takes a while for these messages to appear; cpio
starts out working fine, but eventually bombs.  the problem only occurs
with the -B option.  sun came to look at the problem and, before we had
isolated the -B option as the cause, thought that it was a bad controller,
but replacing it didn't solve the problem.  has anyone seen this problem
before ?  is it a bug in cpio ?  we're running sunOS 4.0 on a 4/280S with
a fujitsu GCR 9 track drive on a Xylogics 472 controller.

thanks in advance,
   monty
   univ of chicago/biological sciences division
   internet: monty at tartarus.uchicago.edu