The late ROMs, eg. the 580 include stuff back to the Mac IIx. :
Of course since you mentioned this, I had to try it in my IIci
It actually plays the startup chime, but the screen stays black. The same behavior I saw when I tried the LC 475 ROM in my IIci too.
This might not be too surprising though. Unless it's hiding from me, I don't see the Display_Video_Apple_RBV1 driver in those ROMs even though it is in other compatible ROMs like the IIsi, 610/650/800, and Color Classic ROMs.
That might be a fun project to try sometime -- hack the RBV driver into the 580 or 475 ROM and see if that allows the IIci to get further in the boot process...or maybe try it in another machine like the IIx that doesn't depend on that driver. Or put a NuBus video card into my IIci.
I'd be pretty surprised if the PowerMac 6100 ROM can actually boot an LC II or IIsi
Agreed. At the very least, it does have the Display_Video_Apple_RBV1 driver so it has that going for it. If I had a IIsi, I would totally test that (and the 660av/840av ROM) for fun. I definitely wouldn't bet on it working though.
It's likely the older machine support only maps the first 1 MB of ROM in the MMU, even if the machine can physically see more.
That's very possible. I should point out that the leaked sources' MMU tables seem to have a ROMMaxSize of 2 MB so at some point Apple upped it from 1 MB. That ROMMaxSize equate is used by several machines, including the Orwell stuff which I believe would apply to the djMEMC and MEMCjr machines. I'd have to inspect the MMU tables in the actual final 660av/840av ROM more closely to confirm. The interesting names from the source that would apply to the 610/650/800 are Template32Orwell and physOrwell, for anyone playing along at home with the SuperMario sources.
They even opened it up to 4 MB (FFRomMax) in TemplateFF32. FF stands for Foster Farms and based on the source it looks like it goes with the V8/VISA/Spice/etc. type machines.
I can't speak for all of these supported ROMs (maybe we could add MMU table parsing
) but in the Color Classic ROM, the Orwell stuff was still only mapping 1 MB of ROM space in the MMU.