Asynchronous Logic: Ready For It?

prostoalex writes "For a while academia and R&D labs explored the possibilities of asynchronous logic. Now Bernard Cole from Embedded.com tells us that asynchronous logic might receive more acceptance than expected in modern designs. The main advantages, as article states, are 'reduced power consumption, reduced current peaks, and reduced electromagnetic emission', to quote a prominent researcher from Philips Semiconductors. Earlier Bernard Cole wrote a column on self-timed asynchronous logic."

Comments

timerless design elements in pentium4?

[sp00nfed]

Doesn't the pentium 4 and most CPU's nowadays have at least some elements of asynchronous logic? And I'm pretty sure that certain circuits in most current CPU's are implemented asynchronously.

Isn't this the same as having a CPU without a timer? (i.e. no MHz/GHz rating).

Re:timerless design elements in pentium4?

[Xeger]

I don't see how your statement is in any way different from mine. I brought up the fact that CPUs make use of asynchronous logic within a single clock cycle, and explained that this does not make them asynchronous machines.

I think you parsed my sentence incorrectly.

I could say "The US might be a free country, but we still have laws to protect others' freedoms from impinging on our own."

Does this mean that I am in doubt, as to whether the US is a free country? No; the US is a free country by definition, the Constitution having defined it as such.

The "Might...but" construct is frequently used in the English language to introduce a fact, and then qualify it.

What's wrong with synchronous?

[phorm]

On the flip side, the millions of simultaneous transitions in synchronous logic begs for a better way, and that may well be asynchronous logic

The advantage outlined here seems to be independant functionality between different areas of the PC. It would be nice if the components could work independently and time themselves, but is there really a huge loss in sustained synchonous data transfer?

From what I've understood, in most aspects of computing, synchronous data communication is preferable. IE, network cards, sound-cards, printers, etc. Don't better models support bi-directional synchronous communication?

Cyclic History

[nurb432]

Isn't this where the idea of digital logic really got started? At least its how it was taught when I was in school.

We even did some design work in async. Cool stuff. Easy to do, fast as hell...

Never did figure out why it never caught on. Except for the difficulty in being general purpose.. so easy of a job with sync logic. And i guess it does take a certian mind-set to follow it.

Re:Cyclic History

[Anonvmous Coward]

"Never did figure out why it never caught on."

I think the internet is a good metaphor of this technology. Take Quake 3 for example. Think about what all it takes to get several people playing over the net. They all have to respond within a certain time-out phase, for adequate performance they have to respond in a fraction of the timeout time, and there's a whole lot of code dedicated to making sure that when I fire my gun, 200ms later it hits the right spot and dings the right player for it.

It works, but the logic to make that work is FAR more complex than the logic it takes to make something like a 'clocked internet' work. The downside, though, is that if you imagine what a clocked internet would be like, you'd understand why Q3 wouldn't work at all. In other words, the benefits would probably be worthwhile, but it's not a simple upgrade.

Intel and asynch clocks

[catwh0re]

A while back I read an article about intel making p2 clockless chips, that performed rougly 3 times(in MHz terms not overall performance) faster.

Intel recognise clockless as the future, and hence the P4 actually has portions designed that are clockless.

Before know-it-all's follow this up with "but it runs at 2.xx GHz", let them please read an article on about how much of your chip is oscilating at that immense speed.

As it's said in the EE industry, "oh god imagine if that clock speed was let free on the whole system"

Beowulf redundant once you have async chips

[Xeger]

In a way, an asynchronous circuit design already is a parallel computer. An asynchronous machine contains many (largely) independent components that communicate with each other in order to solve computational problems more efficiently by breaking them down into small pieces and working on them in parallel.

In this context, your notions of parallel computing will change greatly. Currently, individual nodes in a cluster are islands of computation, separated by (comparably) vast distances. Messages between nodes take orders of magnitude more time than messages within a node.

When you set out to build a supercomputing cluster in the asynchronous world, ideally the entire cluster would be within a single die. Then the latency between nodes would be reduced to microseconds or nanoseconds, and nodes could split work more effectively. The high-speed buses and complex arbitration schemes required for asynchronous computing will be equally useful for designing massively parallel clusters-on-a-chip.

Asynchronous logic vs radiation ?

[renoX]

I'm wondering how asynchronous logic stand up against transiant errors induced by a cosmic ray?

On a synchronous circuit most of the time such glitch won't do anything because it won't occur at the same time the clock "ring" so the incorrect transient value will be ignored.

As the "drawing size" of circuits gets lower and lower, every circuit must be hardened against radiations, not only circuits which must go on space or in planes..

Async research group at Caltech

[mfago]

Here at Caltech the CS department is into this kind of thing.

They've even built a nearly complete MIPS 3000 compatible processor using async logic.

Seems pretty cool, but I'm waiting for some company to expend the resources to implement a more current processor (such as the PowerPC 970 perhaps) in this fashion.

Re:Kurzweil

[imadork]

Why does everyone seem to think that ANNs are the way toward "true AI?" ANNs are superb pattern matching machines. They can predict, and are resilient to link damage to some degree. But they do not think. ANNs have nothing to do with what's really going on in a biological brain, except that they are made of many interacting simple processing elements. The biological brain inspired ANN, but that's all.

I couldn't agree more. I remember reading a comparison between the current state of AI and the state of early Flight Technology. (it may have even been here, I don't recall. I make no claim to thinking this up myself. Perhaps someone can point me to a link discussing who first thought of this?)

One of the reasons that early attempts at flight did not do well is because the people designing them merely tried to imitate things that fly naturally, without really understanding why things were built that way in the first place. So, people tried to make devices with wings that flapped fast, and they didn't work. It wasn't until someone (Bernoulli?) figured out how wings work - the scientific principles behind flight - that we were able to make flying machines that actually work.

Current AI and "thinking machines" are in a similar state as the first attempts to fly were in. We can do a passable job at using our teraflops of computing power to do a brute-force imitation of thought. But until someone understands the basic scientific principles behind thought, we will never make machines that think.

Cute example of Asynchronous logic?

[brejc8]

This is my favorite example of asynchronnous logic.
As the rat speeds up or slows down the chip compensates for it.
Not often that you cant play with toy mice and call it research.