OK Mac-heads:

What actually changed between Mac OS 9.0.4 to 9.1 re: memory management?

Emaculation forums and other sources frequently mention that SheepShaver can't run 9.1 and up because of lack of emulating an MMU.

But Apple's own system requirements for 9.1 say it could run on any PowerPC machine:
web.archive.org/web/2002060203

Am I correct assuming all PowerPC Macs had MMUs then? So if it like wasn't an actual hardware change, what happened here?

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