Re: 1teraflops cell processor possible?

On Fri, 28 Nov 2003 00:03:01 -0500, Robert Myers wrote:
> If you need to haul data a significant portion of the chip width to
> use it once or twice, you're going to get killed on energy costs
> relative to a true streaming architecture.  You can't program that
> away.

You *have* to program it away.  If your program only knows how
to do one thing to each piece of data, then it doesn't matter
how "streaming" the architecture is.

>>Legacy code and legacy coding practices exist.
>
> I don't know in what area you work or have worked, but HPC codes are
> constantly being rewritten to accommodate new architectures.

If HPC codes could be written to accommodate streaming
architectures, then you'd already be seeing 100% FU utilisation
on the existing commodity-processor-based MPP HPC systems.  You
can get (close to) that for some benchmarks (linpack), but that
doesn't seem to be the general case.  The problem is a software
one (at least to a first order of approximation, and on todays
hardware).

My point is that it's all very well to extrapolate hardware
costs out five years and reach certain conclusions, as these IBM
guys have done, but if you still don't know how to get hardware
in that shape to do what you want to do, then its not very
useful, however energy efficient it is.

Perhaps we just have to pay the cost of data movement, until we
figure out how to avoid it.

People hate paying for things that they don't need to, so if
there's an alternative, it will be found.

-- 
Andrew