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Why has CPU frequency ceased to grow? (2014)

software.intel.com

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Re: Why has CPU frequency ceased to grow? (2014)

#241

Post by deepnotderp »

PaulHoule wrote: post #119
mjfl wrote: post #8

I took a class that went over this in depth like 3-4 years ago. Basically the message was that serial performance is saturating, and the only way to get speed improvements in the future is going to be by exploiting parallelism. However, most programmers, and programming languages, remain stuck in a serial-by-default paradigm. I'm surprised that there hasn't emerged a "parallel-by-default C++" kind of language + hardw…

Materials other than silicon can support higher clock rates. From reading the open literature and advertisements by foundry companies, I think you could make a 6502 equivalent processor with Indium Phosphide with 64kb of static RAM that clocks at 30 GHz. With a more refined process you might push 90 GHz and a much more complex processor. Yes, InP is more expensive than Silicon but part of that is the low volume that…

1. Compound semiconductors often suffer from p-type and n-type conduction problems. Plus they're ridiculously expensive and power hungry. They also often lack a native oxide.

2. The problem today in CPUs is not really clock speed but much more the memory access latency, optane is much slower* than DRAM and has much lower endurance.

*Even though silicon HKMG transistors use high k gate dielectrics now, they still use a silicon dioxide interfacial layer.

Re: Why has CPU frequency ceased to grow? (2014)

#243

Post by saltcured »

rbanffy wrote: post #121
BenoitP wrote: post #111

Earlier quoted context omitted.

I'd say exploiting parallelism is not the only way at all. Parallelism is only one way to compute differently. Specialization of hardware to specific workloads will explode in the next years as we can't rely anymore on Moore's law. This will happen on RISC-V, IMHO. We already have these: * Rendering, medium precision mathematics: GPU * Low precision mathematics: TPU * Software Defined Networking: Microsoft is deployi…

Still, if you have only two floats to add and make a decision based on the result, a GPU or a TPU will not help you. Hashing, maybe sorting, blitting and some math could be performed at the on-module DRAM controller level even, without data crossing over the slow DDR4 bus or mangling the CPU caches. I'd love, in fact, to explore such an architecture in a simulator. What would happen to CPU performance if, say, hashes…

Are you aware of previous work on processor-in-memory architecture research? They considered things like this, but I think it stalled out due to semiconductor process and economic practicality.

This article mostly mentions a UC Berkeley effort: https://en.wikipedia.org/wiki/Computational_RAM

This page mentions others: http://www.ai.mit.edu/projects/aries/course/notes/pim.html

Re: Why has CPU frequency ceased to grow? (2014)

#244

Post by madez »

BenoitP wrote: post #111
mjfl wrote: post #8

I took a class that went over this in depth like 3-4 years ago. Basically the message was that serial performance is saturating, and the only way to get speed improvements in the future is going to be by exploiting parallelism. However, most programmers, and programming languages, remain stuck in a serial-by-default paradigm. I'm surprised that there hasn't emerged a "parallel-by-default C++" kind of language + hardw…

I'd say exploiting parallelism is not the only way at all. Parallelism is only one way to compute differently. Specialization of hardware to specific workloads will explode in the next years as we can't rely anymore on Moore's law. This will happen on RISC-V, IMHO. We already have these: * Rendering, medium precision mathematics: GPU * Low precision mathematics: TPU * Software Defined Networking: Microsoft is deployi…

GPU's and Google's TPU's are only capable of certain albeit very important aspects of numerical mathematics. There are other areas of mathematics that have numerical aspects and thus precision, but aren't linear algebra.

Re: Why has CPU frequency ceased to grow? (2014)

#245

Post by Something1234 »

kamaal wrote: post #126
swiley wrote: post #60

Earlier quoted context omitted.

There are limits to how much parallelism will improve things, see amdahl's law.

Sure, but let's start moving towards parallelism first. May be a few decades from now we would be close to breaking those limits.

That law is a fact of life. Its a form of diminishing returns, there's only so much you can do.

Re: Why has CPU frequency ceased to grow? (2014)

#246

Post by jacquesm »

Symmetry wrote: post #159

That was a bit misleading in some ways. First, in pipelining you'll typically measure how long a pipeline steps in FO4s, which is to say the delay required for one transistor to drive 4 other transistors of the same width. Intel will typically design its pipeline stages to have 16 FO4s of delay. IBM is more aggressive and will try to work it down to 10. But of those 10, 2 are there for the latches you added to create…

In case you're wondering, FO = Fan Out.

Re: Why has CPU frequency ceased to grow? (2014)

#247

Post by boomlinde »

adwn wrote: post #187
boomlinde wrote: post #135

Earlier quoted context omitted.

That's a huge simplification not pertaining to the fundamental nature of the brain. Maybe it is in the nature of our consciousness (which in itself is probably only an abstract concept) to perceive the processes it emerges from as a sequence of single trains of thought rather than a chaotic, continuous consolidation of processes both internal to the brain/body and outside of it. You could look at society as a whole a…

> That's a huge simplification not pertaining to the fundamental nature of the brain. I disagree. Conscious thinking is a crucial process that's inherently single-threaded, even though it runs on highly parallel hardware (the billions of neurons). However, I must admit that my point doesn't necessarily contradict pjc's point, and I don't really agree with digi_owl's claim that parallelism is a "wild goose chase".

> I disagree. Conscious thinking is a crucial process that's inherently single-threaded, even though it runs on highly parallel hardware (the billions of neurons).

I don't even know what to make of that. What do you mean by "single-threaded" if at the same time you recognize that it "runs on highly parallel hardware"? If you actually mean that our consciousness emerges from a purely sequential process that happens to go on in a highly parallel system, no, that's clearly wrong. Experience, the fundamental basis of consciousness, actuates many parts of the brain at the same time. They process this information largely independently in different ways, and sometimes those processes result in a clear "train of thought" but most of the time they do not. You can not reason about the inherent nature of our consciousness in terms of trains of thought if you recognize any subjectivity to our experience that exists without reasoning or language. That's a matter of definition, of course, and without agreeing on a precise definition it's probably no use talking about what is inherent about it.

If that's not what you mean, CPU execution models are probably not a very helpful metaphor to explain your idea. The clearly defined layer of abstraction that separates a fully pipelined CPU design built with simultaneously operating logic gates from "single threaded" programs being executed on it doesn't exist in brains. I guess that's what bugs me most about this type of discussion on HN. It seems developers are very fond of taking their (admittedly versatile) hammers and hammer away at anything they can think of, for better or for worse.

Re: Why has CPU frequency ceased to grow? (2014)

#249

Post by ninkendo »

tbrock wrote: post #151
mjfl wrote: post #8

I took a class that went over this in depth like 3-4 years ago. Basically the message was that serial performance is saturating, and the only way to get speed improvements in the future is going to be by exploiting parallelism. However, most programmers, and programming languages, remain stuck in a serial-by-default paradigm. I'm surprised that there hasn't emerged a "parallel-by-default C++" kind of language + hardw…

Golangs’s web server, by default serves every request in a new goroutine (thread of execution) making it parallel by default with no effort on the user’s behalf. Obviously this problem domain is easily parallelized but it’s nice to see parallelism be the refs to standard when possible and reasonable to do so.

Just to be clear, goroutines aren't threads (although they are multiplexed onto threads), and they're only pre-empted at certain points in the go runtime (function calls are the big ones.)

If your request spins in a for-loop doing lots of work without function calls, other goroutines on the same thread won't get a chance to run, and you'll be limited to GOMAXPROCS simultaneous requests. In practice this never really happens though.

Re: Why has CPU frequency ceased to grow? (2014)

#250

Post by mitchtbaum »

stringer wrote: post #134

I've been looking at Haskell, Rust and Go for helping with parallelism but decided to go with a less known language: Pony. Not used actors a lot right now but looks really promising.

Rust has an actor framework among other great projects in its ecosystem:

https://github.com/actix/actix

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