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A New Golden Age for Computer Architecture

cacm.acm.org

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Re: A New Golden Age for Computer Architecture

#31

Post by grkvlt »

pjc50 wrote: post #18
simula67 wrote: post #8

> Today, 99% of 32-bit and 64-bit processors are RISC > Concluding this historical review, we can say the marketplace settled the RISC-CISC debate; CISC won the later stages of the PC era, but RISC is winning the post-PC era It is clear that his assessment is right, but isn't the 99% number too high ? Servers, laptops and desktops still run x86 and they are CISC ( unless you are counting x86 as RISC based on microcod…

> agilely developed chips I feel there's a long way to go there. The economic structure of the industry is against agility because "deployment" remains stubbornly expensive, and the product culture is also much more conservative. > manufacturing also gets open sourced. It's one of the most capital-intensive industries in the world, so I don't quite see how this would work? Libresilicon are offering a 1000nm (not a ty…

Yeah, it's like open sourcing code for 3D immersive visualisation of deep-water seismic survey data, along with the detailed blueprints for the ROV and survey equipment. Awesome enough, sure, but pretty much useless to me. I can build the software like a boss on my laptop, but since I don't have access to any seismic survey data, a CAVE room to view it in, an oceanographic survey vessel, ROV and associated equipment, etc. that's as good as it gets. And, if I had all that awesome oil industry exploration stuff, I'd probably also have a team of engineers building me software anyway, so I don't need it.

My point? Open sourcing stuff with ridiculously huge capital requirements is not that useful, I guess?

Re: A New Golden Age for Computer Architecture

#32

Post by na412 »

insulanian wrote: post #5

I remember being excited about The Machine [1] from HP: "The Machine will be a complete replacement for current computer system architectures. There will be a new operating system, a new type of memory (memristors), and super-fast buses/peripheral interconnects (photonics)." "HP says it will commercialize The Machine within a few years, “or fall on its face trying.”" It seems later happened... [1] https://www.extreme…

HP long ago rebranded "The Machine" to be just a powerful regular computer, since they haven't been successful in making viable memristors at scale.

So they will deliver it, it just won't be anything like what they promised.

Re: A New Golden Age for Computer Architecture

#33

Post by gpderetta »

ghaff wrote: post #23
simula67 wrote: post #8

> Today, 99% of 32-bit and 64-bit processors are RISC > Concluding this historical review, we can say the marketplace settled the RISC-CISC debate; CISC won the later stages of the PC era, but RISC is winning the post-PC era It is clear that his assessment is right, but isn't the 99% number too high ? Servers, laptops and desktops still run x86 and they are CISC ( unless you are counting x86 as RISC based on microcod…

I assume they’re counting them as RISC cores plus microcode that makes them compatible with older x86 CISC designs. Modern x86 is RISC under the covers by any meaningful definition-/and also shares pretty much all the problems.

x86 is not RISC by any meaningful definition. RISC vs CISC has always been about architecture, not microarchitecture. Breaking down instructions into microinstructions is as almost as old as the CPU itself and predates the CISC/RISC nomenclature by decades.

Re: A New Golden Age for Computer Architecture

#34

Post by imtringued »

ghaff wrote: post #23
simula67 wrote: post #8

> Today, 99% of 32-bit and 64-bit processors are RISC > Concluding this historical review, we can say the marketplace settled the RISC-CISC debate; CISC won the later stages of the PC era, but RISC is winning the post-PC era It is clear that his assessment is right, but isn't the 99% number too high ? Servers, laptops and desktops still run x86 and they are CISC ( unless you are counting x86 as RISC based on microcod…

I assume they’re counting them as RISC cores plus microcode that makes them compatible with older x86 CISC designs. Modern x86 is RISC under the covers by any meaningful definition-/and also shares pretty much all the problems.

I don't know why this gets thrown around but it's completely wrong. RISC and CISC are about instruction set architecture. As soon as you have crossed the decoder boundary you are deep into micro architecture territory where the ISA is completely irrelevant because you can use the same techniques regardless of whether you have RISC or CISC.

Now if one would take what you said at face value then it would actually imply that RISC as an ISA is completely irrelevant because it is possible to achieve the same benefits or even beat it despite CISC having the inefficiency of hard to decode instructions and the high cost of a conversion step in the micro architecture. One suddenly realizes that this battle of ISAs is completely futile and the secret sauce is in the micro architecture which is completely divorced from the ISA.

Here are some examples: ARM makes slow ARM chips. Apple makes fast ARM chips. AMD made slow x86 chips in the past but now adopted a faster micro architecture. Intel made Itanium but the chips didn't have any sort of dynamic scheduling so they couldn't deliver the promised performance gains.

Re: A New Golden Age for Computer Architecture

#35

Post by Symmetry »

simula67 wrote: post #8

> Today, 99% of 32-bit and 64-bit processors are RISC > Concluding this historical review, we can say the marketplace settled the RISC-CISC debate; CISC won the later stages of the PC era, but RISC is winning the post-PC era It is clear that his assessment is right, but isn't the 99% number too high ? Servers, laptops and desktops still run x86 and they are CISC ( unless you are counting x86 as RISC based on microcod…

There's an x86 processor in your desktop, but there are many more RISC processors doing things like controlling your hard drive. If you buy an AMD processors there's even an ARM core inside the x86 processor in the Platform Security Processor.

Add in all the microwaves, routers, the many processors in your car, and so on and 99% seems a bit high to me but not unreasonable.

Re: A New Golden Age for Computer Architecture

#36

Post by Symmetry »

gpderetta wrote: post #33
ghaff wrote: post #23

Earlier quoted context omitted.

I assume they’re counting them as RISC cores plus microcode that makes them compatible with older x86 CISC designs. Modern x86 is RISC under the covers by any meaningful definition-/and also shares pretty much all the problems.

x86 is not RISC by any meaningful definition. RISC vs CISC has always been about architecture, not microarchitecture. Breaking down instructions into microinstructions is as almost as old as the CPU itself and predates the CISC/RISC nomenclature by decades.

Many people describe the uOps inside a modern x86 as RISC-like and that's a good analogy. The internals really are much more similar to a RISC pipeline than older microcoded processors were. But it is still just an analogy because you're right about architecture versus microarchitecture.

Re: A New Golden Age for Computer Architecture

#37

Post by Symmetry »

ansible wrote: post #21
pjc50 wrote: post #20

Earlier quoted context omitted.

What specifically is "wrong" with CMOS? Not small enough for you yet? :)

Reaching "the end of Moore's Law" is a super big deal, and I still don't understand why people aren't worried about it more in general. It will cause a crash in the entire tech industry, which will throw the global economy into a depression.

I'm somewhat comforted by the fact that there are fundamental physical limits to computational efficiency[1] which we aren't at yet. MOSFETs look to be just about played out but there are tons of other potential computational substrates. Carbon nanotube transistors, photonics, nano-rod logic, magnetic coupling, DNA computing, etc. We're in for a big interregnum before we get a new paradigm working better than our existing one but there's no reason to believe that progress in computation is ending permanently now.

[1]https://en.wikipedia.org/wiki/Landauer%27s_principle

Re: A New Golden Age for Computer Architecture

#38

Post by imtringued »

wibble10 wrote: post #26
ansible wrote: post #21

Earlier quoted context omitted.

Reaching "the end of Moore's Law" is a super big deal, and I still don't understand why people aren't worried about it more in general. It will cause a crash in the entire tech industry, which will throw the global economy into a depression.

How will reaching the end of Moore’s law cause a crash like this? Do you mean that future requirements will outstrip capacity? I don’t think this has been true for some time, we run a lot more systems and tend to scale horizontally; doubling compute power every n period isn’t a hard requirement imo.

If we ever have an industrial revolution or massive productivity gains again it will most likely involve autonomous machines for things like farming, construction, delivery, transport, etc. All of these things depend on increases in power efficiency or performance. It is possible that we are one or two "doublings" away from achieving this in a mobile package and then suddenly moore's law stops.

For example Tesla is betting on conventional cameras and tries to overcome their shortcomings with computationally intensive machine vision. Tesla's custom chips allows them to have more processing power which means they can install more high resolution cameras and other sensors.

Re: A New Golden Age for Computer Architecture

#39

Post by gpderetta »

Symmetry wrote: post #36
gpderetta wrote: post #33

Earlier quoted context omitted.

x86 is not RISC by any meaningful definition. RISC vs CISC has always been about architecture, not microarchitecture. Breaking down instructions into microinstructions is as almost as old as the CPU itself and predates the CISC/RISC nomenclature by decades.

Many people describe the uOps inside a modern x86 as RISC-like and that's a good analogy. The internals really are much more similar to a RISC pipeline than older microcoded processors were. But it is still just an analogy because you're right about architecture versus microarchitecture.

but microcoding has existed for ever and while uops is probably a very specialized form of microcoding, it still not a new thing.

Also I do not think uops are fixed size as IIRC they can take a variable number of slots in the uop cache, and fix size instructions is pretty much one of the only two remaining differentiating RISC features. The internal x86 microarchitecture is also not load-store, the other one RISC feature, at least in the fused domain, and as far as I understand, in the uop cache.

So, even if we want to abuse the RISC term to describe the microarchitecture, I do not think it cleanly apply to the usual x86 implementations.

edit: this is a pet peeve of mine. It seems I have this discussion every 6 months on HN :)

Re: A New Golden Age for Computer Architecture

#40

Post by Symmetry »

cbkeller wrote: post #6

Interesting article with a lot of great historical context. I think a significant part of the tl;dr is that the end of Dennard Scaling and trouble with Moore's law may mean that the best architecture will finally win out, rather than just the one with the best semiconductor design team behind it. I'm a bit skeptical of the promise of DSAs, though it does seem we're already going that way. Curious what others think on…

The article didn't well on Dark Silicon but the idea is that as you can fit more structures on a chip but can't light up them all for power dissipation reasons it makes sense to include more and more specialized structures you only use for some purposes. With the rise of GPUs and specialized co-processor for things like media decoding and encryption we're certainly well on our way there. It would be nice to have an intermediate between the two in more places, like the Hexagon VLIW DSP that Qualcomm puts in its Snapdragon DSPs. And of course there are the even more specialized matrix convolution processors that everybody is designing and NVidia is now putting in its GPU.

I think the real question is if it will make sense to have FPGAs in wider use. Certainly not until the programming model improves...

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