Author: Johan Klockars (as28-3-8.va.g.bonet.se)
Date: 06-10-2003 09:43
> > No. PowerPC is 100% incompatible with 68k.
> > They have just about nothing in common
> > besides being made by Motorola.
>
> That actually not true...when Apple moves from 68k to PowerPC..they didn't make hole emulator to run 68k software.
It actually is 100% true, which you'd see if you took even a very quick look at the PowerPC.
There is not a single instruction that is the same between the two processors.
Among other things, the PowerPC has 32 general purpose integer registers, not the 8+8 data/address registers of the 680x0, most instructions have two source registers and one destination register, all (or at least nearly all, I haven't checked) instructions are 32 bit long, and the few instructions that might be considered similar are encoded differently, etc.
There might have been some chance of a little overlap if Motorola had designed the PowerPC (though there wasn't with the 88k series, which they did design). However, the PowerPC is originally an IBM design (Power), which was somewhat modified (the PPC601 could run both Power and PowerPC programs (with some instructions trapped and handled in software, IIRC)). Incidentally, all current IBM 'Power' chips actually use the PowerPC architecture (though with extensions in some cases).
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RE: off-beat/off-topic compatability question