Instead a few people choose to pay 20-100x more for boutique PowerPC systems.
You can always use UAE, you don't need to run OS natively on any hardware. You can get this hardware for super cheap and be happy. Choice of PowerPC is as good as any. ARM? "Same difference".
There is plenty of hardware and CPU power to run OS3.9 or 4.1 it is called PC (don't tell anybody it is a secret!).
I don't run my ancient A1200/030 for raw CPU speed... there is NONE of it. Why I want raw speed I use computer cluster at work

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