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A comment on PumpkinOS, a Re-Implementation of PalmOS. Parent comment

Re:PumpkinOS, a Re-Implementation of PalmOS by spc476 on Monday April 08, 2024 @01:44AM (#39966562)
Well, there's also the fact that the MC68000 in the original Mac didn't have an MMU, and it was difficult to add an external MMU to a 68000 system [1]. You could use an MMU sanely starting with the MC68010, and it wasn't until I think the MC68030 that the CPU came with an integrated MMU.

[1] Because exceptions on the 68000 didn't save enough information to restart the faulting instruction. You could get around this, but it involved using two 68000s as insane hack ...

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Re:PumpkinOS, a Re-Implementation of PalmOS by JNRowe on Monday April 08, 2024 @05:54AM (#39968032)
Just to muddy the waters some more there was also an EC variant¹ of the 030 without the MMU.

The EC variant was available right through to the 060, and I'd be curious to know how prevalent the line was. I suspect the EC versions far outnumbered the "full" chips, because they appeared in all kinds of industrial systems. I'm basing that entirely on working for a company that was still shipping products with MMU-less 68k and coldfire this century, not any real data.

¹ https://en.wikipedia.org/wiki/Motorola_68030#Variants

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Re:PumpkinOS, a Re-Implementation of PalmOS by kjs3 on Monday April 08, 2024 @02:59PM (#39972675)
And there's more mud to be found! The 'EC' version of the 68040 & 68060 was "no MMU, no FPU", and there was an 'LC' variant of the 68040 & 68060 that was "MMU, no FPU".

There were huge numbers of embedded 68k family chips shipped, although I've never seen the actual numbers. Folks went from 68000 to 68ec020 to 68ec060 as a (sorta) easy upgrade path. They're still made if you count the 68sec000, and the 68300 line is the spiritual successor.

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Re:PumpkinOS, a Re-Implementation of PalmOS by kjs3 on Monday April 08, 2024 @02:46PM (#39972574)
You could use an MMU sanely starting with the MC68010

Whether the Motorola MMU for the 68010 (the 68451) was sane or not is a matter of some debate. The 68451 was definitely slow and limited (segments, not pages); in the end, most vendors rolled their own MMU out of static RAM and PALs.

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