SunOS booting woes (was Re: Looking for SunOS 4.1.* (sun3) cd image)

First, a belated thanks to the many people who helped me out finding SunOS 4.1.1 images for my Sun3. I now have a CD image that contains both Sun3 and Sun4 binaries, as well as a set of QIC boot tapes for same. Unfortunately, I haven't had a lot of luck getting either to boot on my machine. What I'm getting when attempting to boot from either CD or Tape: Boot: st(0,0,0) Error (PSR = 0x203) Timeout Bus Error: Vaddr: 02000000, Paddr 00000000, Write, FC 5, Size 2 at 0xFEFE0926 When booting from CD, the drive spins up and the access light flickers a bit for a fraction of a second before the above diagnostic is spit out, for tape, the tape is accessed for 15-20 seconds before the error pops up. I'm unsure what this diagnostic message indicates. What I've got set up here is kind of a mishmash of parts -- the chassis is a Sun 3/150 (6-slot VME) and what I'm attempting to run in it is configured as follows: Slot 0: Sun 3/4xx CPU (501-1550) with mono (bwtwo) framebuffer in the P4 slot. Slot 1: 32MB memory (501-1451) Slot 2: Sun3 SCSI (501-1217) I've verified that the jumpers on the backplane are configured correctly (via the guide here: http://www.bitsavers.org/pdf/sun/sun3/813-2038-05_Sun-3_150_Card_Assignment…). I've also ensured that the SCSI chain is properly terminated (at the moment I only have a tape drive or CD drive connected.) The CD drive is jumpered for 512-byte blocks, the tape drive is just a plain old QIC-150 which I've used with Sun machines before. The machine passes all diagnostics and -seems- to be running fine, I just can't get it to boot anything. I have not yet tried netbooting (I don't currently have a *nix machine set up to do the job). I also have a spare 3/4xx CPU and spare 32mb board -- I get exactly the same results with those installed. I do have a Sun 3/150 CPU board, and if I install that I can get it to boot from tape (it's too old to attempt a CD boot) but I don't have any memory for it other than the 4mb onboard, which is pretty tight. I'd love to get the 3/400 cpu running -- anyone have any suggestions? Thanks as always, Josh