Clearing up a major misconception about PowerPC

[silvergunner]

captain carot said:

There is a major part wrong of that.

ARM went that strong because of their licensing model, and yes, they went for ultra low power designs. But those low power designs are terribly weak in some points, eveen right now they're getting better.
Power and PowerPC architecture have been very, very efficient performance per watt wise for years. Which is part of why Power based super computers where the most efficient for years.

Yes, Some Power CPU's where pretty hot, but at the same time had a very good performance per watt.
The die shrinked versions of Cell an Xenon are still somewhat efficient, even if dated. Espresso seems to eat up almost no power. And even the gigantic Power8 has a good performance per watt.

You need to consider that Espresso itself is a 3-core version of a G3 processor, itself having many optimisations over the 10 years since Apple stopped using it. In addition, the Xenon and Cell were custom designs that could be improved over time (by die shrinks and other methods) and not limited to IBM's PowerPC roadmap like Macs - they could be mass produced and gradually improved over several years while Apple needed faster models every 12-18 months.

captain carot said:
The G5 was another story. Apple wanted custom tailerod CPU's for their systems, being developed by IBM. And it seemd that IBM did not want to do so for an actually small customer, chipdesings getting more and more expensive. The G5 design itself was far more efficient than Netburst.
Clocking that chip up like done in the later PowerMacs generated much more heat than originally intended. But that goes for any CPU.
So basically overclocking a CPU (that is what Apple did by default) is ruining your performance per watt.

The "custom tailored cpus" you mention were basically processors promised when the first G5 processors were made - a 3ghz processor (for PowerMac G5) and a lower-power processor (for a PowerBook G5 which never happened). Even at a low speed like 1.6ghz, the G5 was a significant power hog. Both the PowerMac G5 and iMac G5 needed a heavy amount of thermal hardware to keep the processors cold. Same goes for the Xbox 360 and Playstation 3, the former notable for the RROD problem due to (mostly) cooling system failures.

CPU clock does contribute to power gain, correct. Thats why almost every system built this century uses Power Management features, which clock up and down the CPU (even turning it off at intervals) to prevent running at full heat and power usage. Its why battery power on devices depends on use - my laptop battery for example gives me 4 hours internet browsing or 90 mins gaming.

You're right though that IBM refused to honour the promise, claiming Apple was a minor customer. Ironic to think the move away from PowerPC doomed the processor architecture as far as popularity and acknowledgement is concerned, due to Apple having been the most well-known supporter of it.

captain carot said:

With the Core architecture Intel just came to be the better, more practical supplier for Apple, because Intel is making all those CPU's anyway.

Originally Apple investigated both Intel and AMD for x86/x64 processors. They went with Intel because, at the time, AMD didn't have many low-power designs available (the original Core Microarchitecture was based on the Pentium M, itself heavily optimised for mobile devices). If AMD had made an Athlon 64 as power efficient as a Core Duo, we would be using Macs with AMD APUs inside.