Recent content by frontein1

I have a few of these for the Mac Plus. The ICs are probably similar though. Mine are SST 39SF040. You will need to take the BMOW Rominator file (1024KB) and break it into even and odd byte files. Then program each chip individually in the EPROM programmer. I dug around my archives and I...

Just for kicks, I bet we could take this a step further and make the MOD3TEST a bit conditional based on the presence of PGC. So something like this: 1) At start of MOD3TEST, instead jump to some free area in the ROM and probe for PGC. 2) If PGC exists, start MOD3TEST (basically what was...

If you don't have a programmer and a writable SIMM, your best bet might be to buy the Rominator II or another variant. There are a few options available. This way you can get an already programmed SIMM that bypasses the memory check, with some other features included.

Yes your best bet for a 68K era Mac such as the SE/30 is to patch the ROM directly to bypass or modify the memory test.

My IIcx is down for the count right now. But you can drop a IIsi ROM in the IIcx. This would give you a 32-bit clean ROM. So really you probably want a IIsi ROM with just the memory test disabled (and vicariously the ROM checksum altered to not fail) right? If so give the attached a run...

@jmacz I just reviewed your suggested patch - spot on. Write to all memory in Mod3Test then bail. And RevMod3Test really doesn't need to be run either since parity was already initialized. Nice job!

So essentially our theory about the parity bits was probably correct right? Just wanted to confirm.

I was just thinking about this. Wish I had a PGC-equipped IIci to test with :) It is pretty late and I could probably find a better way to explain what I am thinking, but here is a try: That parity bit must have something to do with this. The Mod3 and RevMod3 tests essentially write to all...

I was today years old when I discovered that the IIci has an optional Parity-Generator Chip (PGC). I have similar patches that @jmacz posted for my IIci and it works fine. BUT I do NOT have the PGC chip. I see some extra code in the IIci that is not in the IIsi related to parity checking. So I...

Here is what I did on my SE as an example. There would be a number of different ways to do this. But I just did a NOP NOP for the fall through fail condition. (Offset 26EA) P_ChecksumRom: 26C8 7000 MoveQ.L #$0, D0 26CA 7200...

This. I've started going this route just to keep the routine available. So the routine can still run with the stock checksum, but the only possible return condition is a pass. I'll pull one of the patches out and share it here as a reference.

Just catching up on some old forums related to my favorite topic - ROM hacking.... You know another option would be to patch the actual checksum routine so it always returns a pass value.

It would be really interesting if you could dump out your Rominator ROM to a file. You would need to dump out the full 1024KB from within the Mac OS.... or by using an EPROM programmer. I suspect the chips are OK. But the fact that you hear both chimes indicates the jump to address 421000 for...

Cool discovery @croissantking!

The width of the chips really does make a difference. 8-bit wide chips are nice and easy because you just need to split odd and even. But 16-bit wide you need to byte swap then split by word (16-bits).