I just put an Exabyte 8200 on my 486DX2/66 running NetBSD-1.0.
   I have not been able to read or write to any tape.

   "mt stat" always returns "unknown tape drive type (7)"
   "dd if=/dev/rst0 of=/dev/null" always returns 
	   "dd: /dev/rst0: Input/output error" (plus a report of 0 records/bytes)
   "tar ..." gets the same "Input/output error".

Do you get any console messages when this happens?  Something like:

st0(foo0:4:0): illegal request

perhaps?  I think the 8200 (some firmware revisions, anyway) requires
a hack to read and write mode page 0, similar to the Tandberg 3600 I
have.

You could try enabling the rogue entry for it.  If it doesn't work as
is, changing page_0_size from 5 to 12 might work.  (Someone else
indicated that worked on his drive, but it didn't work on the one I
tried.)