Subj : Re: Running linux in vm on li
To   : Nightfox
From : Derision
Date : Sun Oct 28 2018 01:35 pm

  Re: Re: Running linux in vm on li
  By: Nightfox to Android8675 on Thu Oct 25 2018 17:08:42

 >  An> only difference between a 68k and PowerPC was 16-bti vs. 32-bit, the
 >  An> changet o Intel was significated because the Intel CPU wasn't
 >  An> compabible with 68k/PPC code which is why for a while OSx could run on

 > hmm, I always thought the transition from 68k to PowerPC was also
 > significant because the PowerPC used a different instruction set.  I've
 > always heard Apple had to use emulation to be backwards-compatible with 68k.
 > "Perhaps the most important feature of the new Power Macs was Apple's
 > inclusion of a 680x0 emulator as part of Mac OS, which allowed PowerPC Macs
 > to run most existing software efficiently on the new processors, much as
 > Rosetta would later allow Intel Macs ro run PowerPC software."

It's actually more significant than that, even. The PowerPC's emulation of the
68k is actually at the hardware level, rather than in software. Since the
PowerPC was developed by Apple, IBM, and Motorola, one of it's main functions
was specifically to replace the 68k, and software-level emulation at that point
wasn't anywhere near efficient enough to do so effectively. So the emulation is
built into the chips themselves.

Apple stopped supporting PowerPC after Leopard... but the Classic MacOS -- OS9,
whatever, which still had a lot of native 68k libraries -- would run on any
PowerPC Mac, up to the G5 (the G5 had to do it from within OSX because of a
firmware change; the G4, though, could boot as OS9).

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