I've just put a zip zoom scsi controller in a NetBSD 1.3 pentium machine.
The lines in my config file read

	aic0    at isa? port 0x140 irq 11
	scsibus* at aic?
	sd*     at scsibus? target ? lun ?


Without anything plugged into the scsi bus, the system boots fine.  I
see the following messages in /var/log/messages.

	isa0 at pcib0
	aic0 at isa0 port 0x140-0x15f irq 11
	scsibus0 at aic0: 8 targets
	...
	biomask c840 netmask cc40 ttymask dcc2
	boot device: wd0
	root on wd0a dumps on wd0b
	...

If I plug in a ZIP drive and boot I get an extra line identifying sd0 as ao
100MB ZIP drive, but the system wedges after printing the "biomask" line.  When
it wedges I don't get the ZIP drive probe line written to the log so I haven't
included it here, but it's exactly what I would expect to see.

I guess I can imagine that the kernel could get confused about having
an sd0 and a wd0 when it came to figuring out what it's boot device was.
If this is what is happening how can I fix it?  Initially my config file
had

	config		netbsd root on ? type ?

but I changed that to

	config		netbsd root on wd0a type ffs

in case that made a difference.  It didn't.

Any help would be greatly appreciated.

Duncan