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What happened to clockless computer chips?

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Re: What happened to clockless computer chips?

#31

Post by pjc50 »

gradschool wrote: post #27

The quote from Ken Stevens, whose opinion I respect, makes a compelling argument, and certainly Intel has a lot of expertise on asynchronous design, but I'm wondering if its position is similar to that of Kodak inventing digital imaging in the 1980s. That is, there would be less money for Intel to make in a future where asynchronous design prevails, so there's no incentive for them to develop it. With a properly exec…

> circuits would be more likely to work on the first try because a whole class of hardware bugs wouldn't be a thing anymore

This reminds me of 4GL hype.

I'd say it's the other way round. People have trouble learning synchronous logic design because everything happens in parallel, but it's a set of well-understood building blocks. Whereas asynchronous design is just entirely free of familiar reference points and there isn't quite the same set of standard idioms.

Yes, you get rid of setup/hold violations, but you're going to get a whole new class of problems with the addition that "timing closure" is now a moving target.

Async design in simulation is not some great hidden secret, it's just a trackless jungle. People are welcome to play with it; if you find a great way of teaching async design I'm sure we'd all like to hear about it.

Re: What happened to clockless computer chips?

#32

Post by pg_is_a_butt »

gradschool wrote: post #27

The quote from Ken Stevens, whose opinion I respect, makes a compelling argument, and certainly Intel has a lot of expertise on asynchronous design, but I'm wondering if its position is similar to that of Kodak inventing digital imaging in the 1980s. That is, there would be less money for Intel to make in a future where asynchronous design prevails, so there's no incentive for them to develop it. With a properly exec…

uh... kodak did invent digital imaging even though it was detrimental to them, and they did it in the 1970s. yes, you are a plonker.

you're all idiots.

Re: What happened to clockless computer chips?

#33

Post by qznc »

lightlazer wrote: post #11

Could asynchronous designs improve performance of future CPUs if and when Moore's Law hits physical limits?

> when Moore's Law hits physical limits?

It already did. Sophie Wilson said [0] its 28nm for ever. Scaling further makes no economic sense (unless you really need the space, e.g. in Smartphones).

[0] https://youtu.be/_9mzmvhwMqw?t=34m4s

Re: What happened to clockless computer chips?

#34

Post by Bartweiss »

gradschool wrote: post #27

The quote from Ken Stevens, whose opinion I respect, makes a compelling argument, and certainly Intel has a lot of expertise on asynchronous design, but I'm wondering if its position is similar to that of Kodak inventing digital imaging in the 1980s. That is, there would be less money for Intel to make in a future where asynchronous design prevails, so there's no incentive for them to develop it. With a properly exec…

There's probably truth to that - we talk like companies just miss potential breakthroughs, but they frequently make a conscious decision to abandon a new domain because they have no special expertise there.

I don't think it's much of the story, though. Judging by the Stevens quote, the risk seems to be that async chips would have the same optimization patterns as sync chips - so unlike digital imaging, which started behind and leapfrogged ahead, async makers would be stuck in the past indefinitely.

Intel would be set back 20-30 years on retraining, retooling, and redoing old work, but that could still be worth it if they considered async the way of the future. Unlike Kodak and digital, they would still have enough of their skills and investments transfer to take a massive lead over any other player. So it seems to me that the concern is less "we won't profit", but we "we would never catch AMD's synchronous work".

I wonder if that'll stay true, though; as annual speedups decline, constant factor improvements in power and speed become increasingly appealing. I guess it's a question of whether we're stuck down around 10nm for a long time, or hit a breakthrough in some alternate basis for synchronous chips.

Re: What happened to clockless computer chips?

#35

Post by strictnein »

qznc wrote: post #33
lightlazer wrote: post #11

Could asynchronous designs improve performance of future CPUs if and when Moore's Law hits physical limits?

> when Moore's Law hits physical limits? It already did. Sophie Wilson said [0] its 28nm for ever. Scaling further makes no economic sense (unless you really need the space, e.g. in Smartphones). [0] https://youtu.be/_9mzmvhwMqw?t=34m4s

> It already did. Sophie Wilson said [0] its 28nm for ever.

That's not quite what her slide said. It's that the transistors on 14nm are _currently_ more expensive than those at 28nm, although that may change.

And then she states that only some things will make sense to do at less than 28nm. But a lot of the really big players are already at 14nm or will be there very shortly. Apple, Intel, Samsung, AMD and Nvidia are at 14nm now, either for their newest products or ones to be introduced later this year.

Re: What happened to clockless computer chips?

#36

Post by imode »

one of the main issues in asynchronous design is the idea of gate delays, i.e delays in individual logic gates that compound inside of a circuit.

there are ways of dealing with this. delay-insensitive circuitry, QDI circuitry, micropipelines...

if you're interested as to the "state of the art", as I learned it, look no further than Principles of Asynchronous Circuit Design[1], a fantastic book. a PDF[2] is also available. another fascinating piece of work are Micropipelines[3] by none other than Sutherland.

the main benefit for asynchronous architectures is their ability to be expressed in software. the primitives used (as you'll read) function very much like traditional software constructs based around control and dataflow. this is very easy when your entire architecture is based around pipelines, which can choose to hold and "re-transmit" data.

asynchronous design isn't dead or disadvantageous. we just forgot about it for some reason.

[1]: http://www.springer.com/us/book/9780792376132 [2]: http://www.orbit.dtu.dk/files/2775719/imm855.pdf [3]: https://pdfs.semanticscholar.org/b840/ae4b928964eff41206f89f...

Re: What happened to clockless computer chips?

#37

Post by obsurveyor »

qznc wrote: post #33
lightlazer wrote: post #11

Could asynchronous designs improve performance of future CPUs if and when Moore's Law hits physical limits?

> when Moore's Law hits physical limits? It already did. Sophie Wilson said [0] its 28nm for ever. Scaling further makes no economic sense (unless you really need the space, e.g. in Smartphones). [0] https://youtu.be/_9mzmvhwMqw?t=34m4s

Are you talking about something different here? Kaby Lake is 14nm.

Re: What happened to clockless computer chips?

#38

Post by phkahler »

pjc50 wrote: post #28
phkahler wrote: post #25

Earlier quoted context omitted.

It's a very simple instruction set. Whatever the challenges are with asyc design and verification, the task will be simplified with a smaller/simpler processor design. The open source nature of it also means any company or researcher is free to do what they want with it. Design tool companies for example could create that alternative workflow for async and promote it by saying "look at the results we got on RISC-V" a…

Smaller ARM is quite simple, and as mentioned upthread there was already an async ARM - AMULET. Tool complexity isn't really to do with size or complexity of design, although size affects runtime. It's a question of how accurate the physical modelling is and how well manufacturers trust an OK from the tools. And whether the engineers trust the tools and can use them effectively. There aren't all that many design tool…

>> Less snarky edit: you know that async isn't a magic dust to apply to existing designs, and that someone would have to write an entirely new core targeting RISC-V in an async style?

I have no doubt that will eventually happen. There are lots of RISC-V designs already and more underway. If async is really a win, someone wanting to prove that will do a RISC-V chip with it.

Re: What happened to clockless computer chips?

#39

Post by sqeaky »

qznc wrote: post #33
lightlazer wrote: post #11

Could asynchronous designs improve performance of future CPUs if and when Moore's Law hits physical limits?

> when Moore's Law hits physical limits? It already did. Sophie Wilson said [0] its 28nm for ever. Scaling further makes no economic sense (unless you really need the space, e.g. in Smartphones). [0] https://youtu.be/_9mzmvhwMqw?t=34m4s

We have a really small sample size and forever is a long time.

Re: What happened to clockless computer chips?

#40

Post by petra »

n00b101 wrote: post #23

I asked an Intel chip designer about this and his opinion was that asynchronous processors are a "fantasy." His reasoning was that an asynchronous chip would still need to synchronize data communication within the chip. Apparently global clock synchronization accounts for about 20% of the power usage of a synchronous chip. In the asynchronous case, if you had to synchronize every communication, then the cost of commu…

Maybe. But the benefits could be really big. for example, for mcu's maxim was working on implementing it, and they talked about 85% energy savings.

http://electronics360.globalspec.com/article/4615/maxim-prep...

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