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Comment by mrsebastian | Hacker News Reader

Interesting that you mention Apple/ARM -- don't forget that, eventually, Apple had no choice but to shift from PowerPC chips in its laptops and desktops to Intel. The performance difference was just too vast.

I am fairly sure that the same thing will now happen with x86 and ARM -- it just depends on the timeline.

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That was rather different, as Apple was entirely dependent on IBM and Motorola to produce new chip designs (and Motorola had effectively quit the desktop market). The G5 was actually reasonably competitive with the P4 at the time the move was made, and beat it on some SIMD work. The real trouble was that IBM had repeatedly slipped on its deadlines to produce a low-power laptop-appropriate G5, and the aging G4 architecture just wasn't good enough.

Today, the story is very different. Apple can produce its own SoC designs, as with the A5, or even produce its own ARM _core_ designs, like Qualcomm does, or it can buy from one of a number of healthy vendors who show no signs of quitting ARM anytime soon. If this Intel core had a genuine dramatic performance advantage over the A15 (which it will be competing with, given the timescales), at the same power usage, that would be one thing, but that's far from clear right now.

Apple had to move to x86 because IBM wouldn't invest in development of a fast and low power processor for just one client (Apple) and Intel had a product (Core Duo) ready for them. One client, even Apple, is a very small market. Unit sales of ARM processors combined dwarf x86 sales and there is a huge market for higher performance ARM devices, something that didn't exist for PPC.

That's correct. If you remember, Tim Cook described this limits on PPC based products as a "thermal problem" which is what drove them towards Intel. Presumably, ARM's licenses don't have this problem, in part, as @rbanffy implies, because the ARM architecture doesn't rely on a single source as the PPC did.

It wasn't just that Intel chips were faster. They also consumed less power. Just before the switch, Apple shipped a G5 desktop Mac with liquid cooling built in, which shows just how desperate the situation was for them.

Things are much different now. Intel chips are faster than ARM, of course, but they are also vastly more power hungry. Power consumption matters more than speed in most devices these days (otherwise Intel would already be in everybody's phone) and will likely continue to do so for a long time. Intel shows no sign of being able to reduce their power consumption to the level needed while still retaining decent speed, whereas ARM shows every sign of being able to keep increasing their speeds while keeping power consumption where it needs to be.

Is that 'They also consumed less power' correct?

http://datasheet.digchip.com/205/205-00367-0-970.pdf gives typical power dissipation as 42W @1.8 GHz, 1.3v

For a later design, http://datasheets.chipdb.org/IBM/PowerPC/970/PowerPC-970FX.p..., section 3.1.5 gives 60W for the 2.2 GHz version at 105 degrees Celsius.

http://en.wikipedia.org/wiki/List_of_Intel_Pentium_4_micropr... gives comparable values for the TDP for 2002-era Pentiums.

I get the impression that IBM's data is real max (but 'Maximum power at 85 C is the ONLY value that is guaranteed by Manufacturing Test.'), while TDP may be lower than max (Reading http://en.wikipedia.org/wiki/Thermal_Design_Power)

Or am I overlooking a factor for #CPUs?

I always thought the water cooling was either an effort to decrease noise or over engineering or preparation for more cores and/or more speed (either of which were a necessity to keep up with Intel chips).

I think you're comparing things a little too early. In 2002, things were still very much up in the air. In hindsight, the PowerPC first started showing signs of real trouble when Apple had to de-rate the entire Power Mac G4 line by 50MHz between the initial announcement and the first ship, but it still did fairly well for quite a while. It wasn't until close to the switch when the promised 3.0GHz G5 failed to materialize that the differences really got big. The Intel switch wasn't announced until 2005 and didn't happen until 2006.

I don't have hard data, but as far as I know, once Macs went Intel, they all got significantly faster and cooler.

This was most visible at the top of the line. The last Power Mac G5 had the liquid cooling system and the top end ran four cores at 2.5GHz. I don't know about the liquid cooled model in particular, but the G5s in general were notorious for being noisy due to fans.

The first Mac Pro which replaced it ran 8 cores at 3.0GHz and was known to be astonishingly silent. I personally used one as my main work computer for years and it was impossible to get the fans to run fast enough to be audible unless you disabled the smart controls by e.g. leaving a kernel panic on the screen for a while. Obviously, this could be due to more advanced thermal design as well, but even allowing for that, you have twice as many cores, running at a higher clock rate, vastly faster in most real-world use, and with a much simpler cooling system.

The laptops had a similar story. The PowerBook G4s would get astonishingly hot, while the MacBooks were much less bad (although still not great initially).

Granted that the graphs are coming from Intel, but assuming they're accurate I'd say it's a sign Intel can reduce power consumption and retain decent speed.

http://www.anandtech.com/show/5365/intels-medfield-atom-z246...

Maybe they can, but I'll believe it when they see it. Going by past accomplishments, ARM has done very well in making their chips faster, and Intel has not done so well in making their chips more economical. Certainly there could be a change in the game, but precedent heavily favors ARM in this one.

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