>        And yet, when I try 'mount_cd9660 /dev/rz4c /cdrom' it says
>'mount_cd9660: : Invalid argument'.


Hi,

You mention that the CD is borrowed. 

Are you _sure_ that the CD-rom is jumpered to 512-byte sectors?
(NB: if it's working on a PC, or just about anything except a Sun
or a DEC box, it probably isn't.)

The DECstation PROMs requires that CDs be jumpered to 512 bytes in
order to boot.  I dont know if the Ultrix drivers can handle standard,
2048-byte sector CD-roms after boot, but (AFAIK) the CD-rom driver in
netbsd/pmax is only _known_ to work on 512-byte CD-roms.

(I'm sure someone will correct me if they've tried it and it
works with 2048-byte CDs.)


Sun workstations have the same hardware limitation.   See:
	http://saturn.tlug.org/suncdfaq/suncds.htm
for info on this issue and on jumpering options for some drives.

so, could you please ensure you have a CD-rom that can do 512-byte
sectoring, and then try

	mount -o ro -t cd9660 /dev/rz4a /cdrom

(Note the "-o ro" and the "a" partition.) That _does_ work, verbatim,
on a DEC RRD42 with a couple of random conference-proceedings CDs I
had around.