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Comment by rayiner | Hacker News Reader

It's hot because the tablet and smartphone market exploded, creating a demand for high performance, low-power cores that could be flexibly integrated into SoC's with other parts. With that new market came volume, and in the processor market, volume is important. The reason x86 overtook RISC architectures is that the high volume of x86 chips generated revenues that allowed for massive capital investment in x86 designs. The tablet and phone market is driving a similar process for ARM chips. Right now, there are at least three very well-funded lines of ARM micro architectures: Qualcomm's, Apple's, and ARM's. It's been a long time since a non-x86 platform got that kind of investment.

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You are right that smartphones have drive demand for higher performance and hence more expensive / higher margin ARM CPUs.

But overall ARM volume has been far higher than x86 volume for a long time even excluding all smartphones and tablets.

Most of our x86 servers at work have more ARM CPU's on them than they have x86 cores (most of the harddrives have controllers with ARM CPU's - some of them multi-core etc.). You'll also find it all over the place from washing machines to set-top boxes to microwaves. You find ARM cores in some sd-cards even.

I believe the projected number of cores for ARM last year was around 3 billion. I doubt x86 passed 500 million, which also means that both MIPS and PPC is competing with x86 for second place in number of cores for 32bit+ CPU's. (On the 16 bit or below end you also have surprises like 6502 derivatives shipping in ludicrous volumes)

So x86 has been "hot" for the market for main CPU's in devices consumers recognise as computers, and has been by far the most profitable architecture for a long time. Outside of that, though, it's at best at second place in total volume, and in most non-computer markets it's more likely to place in 3rd to 5th place in volume.

Intel is a big ship to get turned around. When they finally do they will end up more than competitive.

That, and because historically, the ARM instruction set has always been the gold-standard power-efficient 32-bit architecture. Especially in thumb mode.

Open-source software and the extreme efficiency goals of data centers make an interesting alternative to x86 now.

If you look at it from the perspective of expressiveness, the CISC-ness of the x86 ISA also allows far more opportunity for hardware-level enhancements than a RISC style one: the code density is higher, meaning better cache usage and less memory bandwidth needed (especially with multiple cores), and there's still a lot of relatively complex instructions with the potential to be made even faster. RISC came from a time when memory bandwidths were higher and the bottleneck was instruction execution inside the CPU, but now it's the opposite; memory bandwidth and latency is becoming the bottleneck. There's only so much you can do to speed up an ARM core without adding new instructions.

Linus has some interesting things to say about this too: http://yarchive.net/comp/linux/x86.html

It's pretty weird to think that x86 gives Intel any advantage over ARM.

Let's see: x86 code density is horrible for a CISC, there is hardly any advantage over ARM, which does great being a RISC. Also remember that the memory bandwidth is primarily a problem for data, but not code. ARM64 is a brand new ISA, it's the x86 ISA that is a relict from the times when processors were programmed with microcode. Intel is doing a great job to handle all this baggage, but to claim that the ISA gives Intel an advantage is ridiculous.

And finally, Linus has been an Intel fanboy since day one. Go read the USENET archives to find out. He received quite a bit of critique because the first versions of Linux were not portable but tied to i386.

x86 code density may not be optimal but it's better than regular ARM - only thumb-mode can beat it, and just barely.

> Also remember that the memory bandwidth is primarily a problem for data, but not code

RISCs, by design, need to bring the data into the processor for processing; but I see things like http://en.wikipedia.org/wiki/Computational_RAM being more widely used in the future, where the computation is brought to the data, and this becomes much easier to fit to a CISC like the x86 with its ability to operate on data in memory directly with a single instruction. Currently this is done with implicit reads/writes, but what I'm saying is that the hardware can then optimise these instructions however it likes.

The underlying principle is that breaking down complex operations into a series of simpler ones is easy, combining a series of simpler operations into a complex one, once hardware can handle doing the complex one faster, is much harder. x86 lagged behind in performance at the beginning because of a sequential microsequencer, but once Intel figured out how to parallelise that with the P6, they leapt ahead.

Linus being an Intel fanboy has nothing to do with whether x86 has an advantage or not. But even if you look at cross-CPU benchmarks like SPEC, x86 is consistently at the top of per-thread per-GHz performance, beating out the SPARCs and POWERs, and those are high performance, very expensive RISCs. I'd really like to see whether AMD's ARMs can do better than that.

Interesting, but I wonder how much faith to put in Linus' claims given the demise of Transmeta.

I already start to feel like a grandpa talking about 8080, x86 processors. The next generation may not even remember what x86 is. The movie mimzy predicted intel to stay there until the far future, when they are able to fabric self-assembling smart chips.

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