I've been playing with a PowerTec SCSI card and a DAT. I'm tried using
a -current kernel as well as an older 1.3G kernel.

If the machine boots without a tape in the drive any attempt to access a
tape subsequently inserted will give an Input/output error. Is there
any way to reset this state?

When the machine has booted with a tape in the drive then I've successfully
tried cd /; tar -cp * to write a tape. So I thought I'd have a go with
dump, but this dies with:

DUMP: master/slave protocol botched - didn't get pid of next slave

Has anyone used a tape drive to run a success backup strategy with
NetBSD/arm32? I don't expect it to be particularly useful with the current
SCSI drivers for the RiscPC, but I was pleasantly surprised that the
initial tar worked.

Aside:

After a couple of crashes with a -current kernel in some of the pmap
code, I tried to reboot and the machine gave the following error messages
(with either kernel). The messages were repeated in seemingly random order
about 10 times each.

uvn_io: note: size check failed
 Data abort: 'Translation fault (page)' status=007 address=00031000 PC=00001084
Failed page fault in kernel
Segmentation fault

As an test of faith as much as anything, I restored from my previous
tar dump and it fixed the above problem. Hurrah!

-- 
Dr. Stephen Borrill