[rescue] OpenBSD on an SS5 - argh!

[Micah R L]

I've recently acquired four SPARCstation 5 machines for cheap cheap, and 
I'm looking to put OpenBSD on one of them to play with. It took me a 
long time to get it to boot from the install media. I had to "dd 
if=/dev/zero bs=1k count=10 >> cd35.iso" and reburn the boot cd to 
escape the error "bootxx: short read, Program terminated"

 From this point, the install process went easily enough, but when I 
halted the system and got the PROM promt again, I could not start the 
system from disk. The install instructions say to do
    ok setenv boot-file bsd
    ok setenv boot-device /sbus/esp/sd at 0,0
    ok boot
, but I just get:
    Boot device: /sbus/esp/sd at 0,0 File and args: bsd
    Can't open boot device

Elsewhere I have seen that I should just be able to say
    ok boot disk
, and that also doesn't work; I get
    Boot device: /iommu/sbus/espdma at 5,8400000/esp at 5,8800000/sd at 0,0 File 
and args: bsd
    Illegal Instruction

I have tried switching 0,0 to 3,0 due to SCSI strangeness about these 
systems, and that doesn't work either.
Does anyone have any clues? This is getting obscenely irritating.