On Sunday 18 March 2007 16:18, Nicolas Boulay wrote:
> > > > >   3) wait for AMD to sell a AMD64 30,000+ x16 CPU?
> > > >
> > > > Impossible, light isnt that fast.
> > >
> > > IIRC they now have 6000+ x2, so they only have to find a 5x
> > > speed improvement.
> >
> > Yes, but 4GHz is about the limit how fast chips with
> > 2x2cm can be clocked. And even that needs very carefull
> > design of the clock distribution and signal routing.
> > Keep in mind that 2cm is about the distance a signal
> > can travel within one clock cycle (depends a lot on
> > the actually used wire model). And then you still
> > need some safety margin to reliably operate the chip
> > under all specified conditions.
>
> A pentium 4 use double frequency ALU (this permit to simulate 2 ALU).
> Pentium 4 at 3 Ghz exist sine more than 4 years. 3 Ghz cpu imply 6
> Ghz ALU in the pentium 4.

I doubt that that ALU is 2x2cm though, it's probably very small with a 
localised clock. The Cell chip would perhaps be a better example; it's 
supposed to go up to 5 GHz I think. But then, that's basically a bunch 
of loosely coupled DSPs together with a simple PPC core (which I don't 
think runs at full speed actually, but I'm not sure), so that's another 
kettle of fish.

I do think there's work going on about multiple clock domains and 
clockless computing, but I don't know whether they are anywhere near 
production on that.

Lourens

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