SCSI issue

I have a sparc station 20 that I recently bough a cdrom for so that I
could install debian linux. At this point there is not a functioning os
on the computer.

At the OK prompt when I type "probe scsi" I am told that only the cdrom
is detected and then it hangs. On the two hard drives previously
installed there is a total of one jumper in place. On the cdrom no
jumper are in place.

I am sure this is a simple matter of the scsi variant of master/slave or
something like that, but I would rather not experiment with jumpers.