Alex, when you mentioned the Mac, were you referring back to the days when Apple did PPC to x86 translation on the fly, at load-time? (Or for all I know, earlier than JIT, because they may have cached stuff beforehand on an earlier run? You can also compile MSIL to native x86 code can you not ? And I presume it puts the result into a cache so it can remember whether or not a particular module has already been compiled. DEC did VAX to Alpha code translation too in the early 1990s iirc. )
You’re right, need to rule out the effects of availability of better instructions and stick to truly identical code. Allowing for code differences that take advantage of instructions set and register set size improvements means answering a different but also interesting question.
And I’m not interested in power, just total energy consumed by a particular truly CPU-bound job, regardless of how long it takes. Machines that are truly static, which I think might be rare, [don’t know ? that’s a very good question], can get a job done quicker on machines with a higher clock rate and then sleep sooner with the clock turned down to literally 0 Hz for longer (Like all of Psion’s machines 35 to 20 years ago) so the total energy consumed may remain roughly the same pari passu.