ROM SIMM incompatible with specific SE/30?

[Macobyte]

Here’s a mystery I’m trying to figure out.

I have an SE/30 with a stock logic board with a BMOW ROMinator II and 128MB of RAM. Also in this machine is a 50MHz DiiMO and a MacCon Ethernet card, and it all works perfectly.

I had a spare SE/30 logic board with trace damage which I sent to Will of CayMac Vintage to transplant to a SE/30 Reloaded board (which he did a fantastic job on, by the way).

I have a spare stock SE/30 ROM and 8x 1MB RAM SIMMs (8MB total) which go with this spare board and I sent along with it to Will for use/testing.

Before I sent the board and ROM and RAM, I tested the (stock) ROM SIMM in my good board and got a bus error on boot, after the “Welcome to Macintosh” screen. Thinking it didn’t like the 128MB of RAM, I swapped in the eight 1MB SIMMs. Same result. Either set of RAM worked fine with my ROMinator II. Advising Will of this I sent everything on. He transferred everything to the Reloaded board and tested it with my stock ROM and 8MB of RAM in his SE (effectively a SE/30 with my Reloaded logic board connected) and it worked fine. I believe he even hooked up his TechStep to verify everything was functioning correctly.

I received the Reloaded board back and it works great; I swapped it into my SE/30 and installed my usual configuration of the ROMinator II, the 128MB of RAM, and my DiiMO and MacCon. Curiously, I then swapped my stock ROM SIMM in (with the 128MB of RAM), and I got the same pesky bus error again. So on my other, stock logic board which was in my SE/30, I installed the stock ROM SIMM and the 8MB of RAM and tried that… again with a bus error.

This stock SE/30 ROM SIMM has been tested in two different known-working logic boards, each with 8MB and 128MB of RAM installed, and it has thrown up a bus error in every case except when the Reloaded board was installed in an entirely different SE(/30) enclosure, in which case it worked fine.

Given the bus error message, you may assume it has something to do with the boot drive, and that is another key difference as my SE/30 has an internal SCSI2SD v5.2 running System 7.5.5 and Will was booting off an external BlueSCSI running (I believe) 7.5.3. However, I suspected the boot volume could be the culprit when I originally tested the ROM before sending everything to Will… I swapped in the Mac’s original, working Quantum Fireball drive running 7.5.5; I got a bus error there as well.

So what’s the culprit here? Could there be something unique to only my SE/30, not related to any component on the logic board, which could cause a bus error with a stock ROM while not causing any issue at all with a ROMinator II (and 128MB of RAM and a DiiMO) installed? How do I even begin to troubleshoot this? Any suggestions or input are welcome and thanks in advance.

 

[Macobyte]

Forgot to mention: If I hold down shift and reboot with extensions off as the bus error message suggests, I get the same bus error message again, so it’s not an extensions issue.

 

[jeremywork]

Perhaps something in your system folder requires a 32-bit clean ROM. The Rominator would’ve come flashed with one, and the stock SE/30’s isn’t. Maybe when testing in the other machine it was booting from a simpler ssw.

 

[Macobyte]

Perhaps something in your system folder requires a 32-bit clean ROM. The Rominator would’ve come flashed with one, and the stock SE/30’s isn’t. Maybe when testing in the other machine it was booting from a simpler ssw.

I should have worded the bit about also trying the Quantum Fireball with a little more detail… It has an unpatched copy of 7.5.5 and booting off of that drive still causes a bus error with the stock ROM installed. So I don’t think it’s related to the System Folder.

 

[croissantking]

In order to use System 7.5.5 with a Rominator II you would have had to patch the system suitcase file at some point with ResEdit. Once you have done this, you can't put the stock ROM back in the machine and boot off that install. You'll get the bus error you're seeing.

Edit: just noticed you say it's unpatched. Are you absolutely sure?

 

[Macobyte]

In order to use System 7.5.5 with a Rominator II you would have had to patch the system suitcase file at some point with ResEdit. Once you have done this, you can't put the stock ROM back in the machine and boot off that install. You'll get the bus error you're seeing.

Edit: just noticed you say it's unpatched. Are you absolutely sure?

Correct; please see my latest reply to a similar comment in the thread. Is there anything else which can cause this bus error, something hardware-related to do with either the drives or power supply? Considering the error occurs with that ROM with different boards, sets of RAM, and boot drives.

 

[croissantking]

I doubt it would be anything related to either the PSU or analog board.

Can you try booting off a disk tools 7.5.3 floppy to rule out SCSI issues?

 

[croissantking]

Could the ROM SIMM be defective or not making good contact with the socket?

 

[Macobyte]

Could the ROM SIMM be defective or not making good contact with the socket?

This was Will’s latest guess too and we were exploring it when we had to call it a night; perhaps today I’ll have some time to dig deeper… That ROM worked fine with the same board in his SE so I know it’s not defective. I supposed contact could be the culprit however the only change other than the machine it sits in was him shipping the board back to me; it was very well-packed and was shipped without the ROM and RAM installed. Also, that SIMM socket works perfectly with my ROMinator II and the stock ROM sits very securely in it as well. For all of these reasons I’m inclined to believe it’s getting good contact and the issue lies elsewhere.

 

[mikes-macs]

A Rominator II will by-pass the memory test while the stock ROM will not. Perhaps it’s the RAM that’s faulty or mixed speeds. Try using only four of the 16 MB SIMMS in Bank A with nothing in Bank B using the stock ROM without Mode32 and an unpatched system 7.5 . Verify if the ROM works because I actually have a stock SE/30 ROM that does not work, so they do become defective. I verified this using a genuine Mac IIsi ROM.
It should be noted that the Rominator II causes a Macintosh SE/30 to be less picky about RAM.

 

[Chopsticks]

try booting off a system 7.0.1 install or floppy disc
id be interested to see if if boots up or fails differently.
for some reason the 53C80 is coming to my mind as a possible culprit

 

[Chopsticks]

forgot to mention too that the se/30 really needs an internal scsi drive to be properly terminated and if you have an external scsi chain make sure the last psychical device is terminated too, otherwise you will get bus errors.
system 7.5.x is much more tightly controlled then 7.0.1 was with the scsi boot up routines. if something is marginal then system 7.5.x is much more likely to complain