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Apple was threatening MFM-only/manual eject floppies around the same time, though it never shipped.

This reminds me of how early 16MB 30 pin SIMMs based on 400 mil chips were very tall as well. It is a shame that by the time 16Mbit chips was catching on the Mac IIfx was obsoleted by the Quadra.

As a side note, this also reminds me of 400 mil vs 300 mil 16 megabit DRAM chips (even 350 mil 4 megabit DRAM chips often barely fits). There is a reason why Apple switched to 72 pin SIMMs by the time of the LC III.

Anyone knows where the odd 512k and 2MB 30 pin SIIMMs came from?

I wonder if any Macintosh LC shipped with 6.0.6.

Exactly, and the Lisa was no exception.

Just looked at "MC68000 Group 1 and 2 Exception Stack Frame" and "MC68000 Bus or Address Error Exception Stack Frame" and the two are completely different, requiring a tons of code in the Lisa bus error handler.

As a side note, the proposal suggest raising the clock speed of the 68010 to 10Mhz. Given that the speed of 68010 tends to lag behind a 68000 anyway...

I don't think this is how bus errors work on the 68000. You can't directly RTE from a bus error on the 68000. Remember that every intersegment call on the Lisa triggers a bus error and I believe often used special code sequences..

The bus error changes are the entire point of the 68010.

That being said I do wonder how the MC68451 compared to Lisa's segmented MMU. But AFAIK the 68451 dates before the 68010, right?

The 68010 did not include an MMU and I am not talking about changing the MMU. I am talking about the new support for handling bus errors for example where you can just RTE.

It would have greatly simplified the Lisa OS.

The sad thing is the Lisa 2 was close to supporting the 68010 already: https://lisalist2.com/index.php?topic=43.0

0178 is the original Mac II ROM. 067C is the ROM used in the Mac IIci and later. There is also 077D (SuperMario), but A/UX never supported Macs that used this one.

I think Rene Vega claimed that the Mac OS 8.6 and later MP nanokernel once supported it.

Yes, System 7.5 is what introduced PC Exchange.

http://oldcomputers.dyndns.org/public/pub/rechner/apple/modern_mac/macos/0306678sys75800.pdf Do anyone have copies of this.

They are generally contiguous on pre-IIci machines. I believe that the IIci always dedicate 64MB to bank A and use the PMMU to remap.

It would be easy to support both with the same ROM code, and I believe that the ROMs are exactly the same.