Henry Bent wrote:
> 
> No matter what I do, the RRD42 refuses to give anything but "?IO:
> 3/rz4/netbsd  (bb rd)".  This is a CD that I've booted other machines from,
> so that's not the problem.

I had exactly the same problem with two other RRD42s. I guess your drive
is dead.
Should you find a solution though, let us know. I still have one of those
dead drives here.

> --
> KN02-BA V5.7c    (PC: 0x0, SP: 0x801ffec0)
> >>
> --

Are you sure that there is something too boot one this drive?
What do you get when you try this?

boot '3/rz3/vmunix -a'

HTH
Dennis