Re: a dozen cpu's on a chip

John Larkin wrote:
On Wed, 14 May 2008 19:50:42 +0100, John Devereux
<jdREMOVE@xxxxxxxxxxxxxxxxxx> wrote:

Your "lots of little cores" scheme is not much use in this scenario,
since all the near-idle tasks could have been done in a single
multitasking core anyway, and the (likely single) heavy duty task runs
*really slowly* on one of your little cores.

He also gets a very nasty I/O contention bottleneck problem thrown in for free. If the prime objective is to waste as much power and silicon with no useful payback then it would be a near perfect design!

What is actually needed is a single core that is just about as fast as
possible. Only when it runs up against practical limits is it then
worth going to 2-core, 4-core etc. And you can then rewrite the "heavy
duty task" to split itself over multiple cores. But the most efficient
scheme would still be to have all the lightweight tasks on one of the
cores, and the single heavy duty program spread over the remainder.

And this is what we have.

Of course this is what we have. But what will we have 10 or 20 years
out?

In this particular case for desktop PCs we have reached a point where the available hardware is more than adequate for most peoples needs. Word processing and basic image manipulation doesn't really tax modern kit - even video editing is easy on a PC now.

It can run HDTV or games at insane frame rates - we may see more 3D capable display hardware for gamers which will double the bandwidth requirement and that is probably the endgame - at least until some killer consumer app requiring an order of magnitude more CPU comes along.

In case you haven't noticed PCs have now become mass consumer items sold just like TVs, fridges, ovens. And they do not have to obey Moores law (even if bleeding edge kit continues to get faster).

Ever more memory is guaranteed until 4GB is standard and there may then be a clean break when 64bit OS's come of age but the hardware is now good enough to satifsy most users needs as it is.

So far there are no killer apps that force a migration to 64bit OSs. I am tempted for running some chess puzzles - having 64 bit registers makes for very fast 8x8 bitboard implementations.

The GHz race is slowing down to a standstill; everybody is going to
more cores to get more mips per chip. The new PR race will be for
number of cores, not GHz.

I doubt that. Having more than 4 cores for a general purpose mainframe has been the downfall of major players in the past. I expect 4 or maybe at a pinch 8 cores to be the practical limit in normal domestic PCs.
(and don't be an early adopter of N>4 unless you enjoy lots of strife)

Unless you have software that is designed to run efficiently on multicore CPUs you just end up with very expensive wasted resources.

If there is a new PR race I am more inclined to think it will be along the lines of effective MIPS/W with CPUs that shutdown or throttle back when demand is low rather than galloping through the idle task at 3G instructions per second. Portable devices capable of lasting many days on a single recharge and streaming video for instance. ARM already have some potent offerings in this market segement.

FTTH is coming; soon a good hunk of the population will have gigabits
per second pouring into their houses.

But what will they do with it? You can quickly fill a TB disk, but you can only watch HDTV at realtime human compatible speeds.

Nanometer geometries are happening, but still with UV lithography. So
yields are going to suffer, and yields on a single-core CPU with a few
billion transistors won't be great.

Single core has reached its limits for now. Dual core and quad core will certainly improve things for those of us that hammer PCs and gamers (but the latter also need exotic dedicated display coprocessor hardware).

Heat sinks probably won't get much better.

So, things will stay the same?

They probably will not evolve so rapidly as in the recent past. Memory getting cheaper means is will soon be possible to populate the entire 4GB address space of 32bit Doze (minus gaps). Disks the same. We will see faster solid state magnetic and flash drives and maybe other memory technologies make it to market that are still toys in the lab.

I don't think things will stay the same, but I don't think your idea of a processor for every task is even remotely where things are headed.

Regards,
Martin Brown
** Posted from http://www.teranews.com **
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Relevant Pages

  • Re: a dozen cpus on a chip
    ... Twittering, blogs, yes you _REALLY_ need 10 extra cores for that. ... will always multitask, because that's efficient. ... to do something that takes a *lot* of CPU power. ... and the single heavy duty program spread over the remainder. ...
    (sci.electronics.design)
  • Re: a dozen cpus on a chip
    ... Twittering, blogs, yes you _REALLY_ need 10 extra cores for that. ... will always multitask, because that's efficient. ... to do something that takes a *lot* of CPU power. ... and the single heavy duty program spread over the remainder. ...
    (sci.electronics.design)
  • Re: a dozen cpus on a chip
    ... Twittering, blogs, yes you _REALLY_ need 10 extra cores for that. ... will always multitask, because that's efficient. ... to do something that takes a *lot* of CPU power. ... and the single heavy duty program spread over the remainder. ...
    (sci.electronics.design)
  • Re: a dozen cpus on a chip
    ... John Larkin writes: ... Twittering, blogs, yes you _REALLY_ need 10 extra cores for that. ... Your "lots of little cores" scheme is not much use in this scenario, ... and the single heavy duty program spread over the remainder. ...
    (sci.electronics.design)
  • Re: a dozen cpus on a chip
    ... Twittering, blogs, yes you _REALLY_ need 10 extra cores for that. ... and the single heavy duty program spread over the remainder. ... The GHz race is slowing down to a standstill; ... yields are going to suffer, and yields on a single-core CPU with a few ...
    (sci.electronics.design)
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