I'm trying to install NetBSD/sun3 (as of March 3) on my 3/260.  I've
installed all of the tar files (running under the Sun miniroot), then
installed the boot program, done a 'MAKEDEV all', and created an
/etc/fstab.  When I try to boot NetBSD, it get most of the way through
the boot process and then hangs for 60 seconds or so, and then panics
with "cannot mount root":

..(info deleted)
si0 at vmes0 addr 0xff200000 level 2 vector 0x40
scsibus0 at si0                                    <-- LONG PAUSE HERE
vmel0 at mainbus0
root on sd0a
swap on sd0b
dump on sd0b
panic: cannot mount root
Stopped at    _Debugger+0x6   unlk    a6
db>

It is possible that my /etc/fstab is bad, since I had to piece it
together from info in the man pages.  Here's what I came up with:
/dev/sd0a / ufs rw 0 1
/dev/sd0b none swap sw
/dev/sd0g /usr ufs rw 0 2

Does anyone have any hints? 
In case it's useful, here's a description of the machine:
3/260, 8M, cgthree, SCSI controller, 1/4" tape, 324MB Maxtor 7345S.

Thanks in advance for any help!

Evan Rosser
ejr@cs.umd.edu