Intel Dismisses 'x86 Tax', Sees No Future For ARM

MrSeb writes "In an interview with ExtremeTech, Mike Bell — Intel's new mobile chief, previously of Apple and Palm — has completely dismissed the decades-old theory that x86 is less power efficient than ARM. 'There is nothing in the instruction set that is more or less energy efficient than any other instruction set,' Bell says. 'I see no data that supports the claims that ARM is more efficient.' The interview also covers Intel's inherent tech advantage over ARM and the foundries ('There are very few companies on Earth who have the capabilities we've talked about, and going forward I don't think anyone will be able to match us' Bell says), the age-old argument that Intel can't compete on price, and whether Apple will eventually move its iOS products from ARM to x86, just like it moved its Macs from Power to x86 in 2005."

Comments

Speed versus complexity

[girlintraining]

You know, we had the same argument with RISC versus CISC architecture. And we know who lost that one. Badly. And the reason for that is because the bandwidth outside the processor, the I/O, is so damnably slow compared to what's possible on the die itself. That's why the data transfers to and from the CPU are only about 1/30th or less the speed at which the CPU runs internally. The only logical course of action is to do as much as you can on each byte of data coming off the bus as you can. Besides, look at Nvidia's GPU cores: They throw hundreds of cores onto the die, but it eats hundreds of watts as well. Massively parallel and simple instruction sets don't appear to translate into energy savings.

Re:Speed versus complexity

[Chas]

Intel won the CPU wars because of manufacturing, not because of a superior instruction set.

There's nothing inherently "superior" about ARM or PPC instruction sets.

Each has its strengths and weaknesses and prescribed methods of capitalizing on the former while working around the latter.

Is x86, possibly, more inelegant than ARM or PPC? Maybe. Then again, what exactly is so elegant about a "catch all" platform where the basic processor architecture can change wildly between manufacturers, leading one to require many "flavors" of code simply to cover multiple vendor platforms?

x86 may be ugly and hackish. But it's probably THE best documented platform in history and has very VERY few platform segregation points.

Re:Speed versus complexity

[Darinbob]

Power-wise the argument is right. There's very little difference between the two instruction sets that makes one more power efficient than the other. However in practice the difference is that most Intel x86 family chips are optimized for high performance (desktop) where as most ARM chips are optimized for cost and efficiency (low power embedded systems, phones, etc). ARM probably has more experience in the chip design in making things smaller but as it ramps up into faster desktop or tablet oriented CPUs it is going to lose out more.

It really does come down to software ultimately I think. Software needs to do minimal work if it wants to save power; stop checking the net every minute to see if there's an update, put the CPU to sleep when not in use, use interrupts instead of polling, do more in a compiled low level language and less in a byte code interpreted language or scripting language, keep things small, and don't let Microsoft touch you. As soon as you start demanding the ability to run MS Office then you are giving up on power savings.

Re:Speed versus complexity

[yakovlev]

For a "modern" CPU the instruction decoder is an absurdly tiny part. This is because the branch prediction, caches, issue queue, regfiles, etc. are all much larger or at least the same size.

This isn't nearly so true in a super-low-power mobile design. The instruction decoder size for a given instruction set architecture is pretty much a fixed size per decode pipe. This means that in one of these tiny mobile chips the relative size of the decoders is dramatically larger. A super-low-power chip dramatically reduces the sizes of the caches and branch prediction, reduces the size of the regfiles, and often eliminates the issue queue. It probably also removes a decode pipe, but the relative reduction in decode size is much smaller than the relative size reduction in other areas.

The limited register set absolutely hurts x86 on power usage, perhaps more than the decoders do, since it forces more data cache accesses for register spills and fills.

Now, I'm not saying that x86 is necessarily worse than arm on power usage, as the richer instruction set may have other advantages such as reducing instruction cache miss rate which can be used to improve IPC which can be spent to lower frequency and reduce power. Also, microcoded instructions may turn out to be more power efficient because they don't have to access the instruction cache every cycle.

None of this considers the fact that Intel has the best fab technology in the world. This means their processors will be a generation more efficient than everyone else's, which is probably more than enough to counter any "x86 tax" which the instruction set incurs.

Re:Speed versus complexity

[hairyfeet]

While this is true frankly its only been fairly recently that either AMD or Intel gave a crap about power, and look at how far they've come? Intel has gotten Atoms to less than 3w, AMD has gotten dual cores AND a decent GPU down to 9w in the C Series bobcats, and of course the Intel CULV Core chips can do a scary amount of processing on I believe their latest are sub 10w. Now according to ARM their A9 duals are just a hair under 2w. that of course isn't counting the chips like the hardware decoders typically found with ARM because it just can't do as many IPCs as X86.

So I'd say as folks demand more and more performance out of their mobile devices the advantage will probably swing to Intel.Tthey have the fabs and have been able to shrink quicker than anybody else so 1 or 2 more shrinks and its gonna be pretty damned close and with such a huge IPC difference between X86 and ARM in a damned close race I'm sure many would rather have the faster Intel chip, AMD will most likely be stuck at the niche they are now, at least as long as they stick with the faildozer "half a core" design so that just leaves Intel and ARM and with the money, the fabs, and the R&D budget that Intel has i think it'd be crazy to call it for ARM at this stage of the game.

After all it wasn't too long ago that everyone was making netburst space heater jokes and look how quickly that situation changed. I seriously doubt Intel is gonna sit this one out and when looking at their past record there is no reason to think they can't make a chip that'll compete.

Re:Speed versus complexity

[naasking]

There's nothing inherently "superior" about ARM or PPC instruction sets.

Superior to x86? Sure there is. x86 is a mish mash of instructions many of which hardly anyone uses except for backwards compatibility, but that still cost real estate on the CPU die. That's real estate that could be spent on bigger cache or more registers. ARM is a much better instruction set by comparison.