Hmmm, well then, let me give you my standard lecture on that subject.
Normalizing the clock rates of machines designed to achieve different
clock speeds is an odd exercise. There's a 400 MHz gap between Intel's
fastest CPU (Pentium 4 Northwood) and AMD's fastest. That gap exists,
not because AMD doesn't care about clock rate, but because the Pentium
4 was designed for 2.2GHz and the Athlon was not.
What makes this a slippery subject to discuss is that that higher clock
rate comes at a price: CPU efficiency. For the same reason that a race
car doesn't get the fuel economy of a compact car, a machine designed
to max out the circuits doesn't get the instructions-per-clock efficiency
of a machine designed for a slower clock. The faster clock demands more
pipeline stages, each stage implies latch/skew/jitter overhead, more
stages makes the branch mispredict penalty higher, and so on.
Normalizing the clocks is equivalent to pretending the slower-clock CPU
somehow found a way to achieve the higher clock without the attendant
overhead. Nice work if you can get it. But I don't know how to do that,
and I think if AMD did they'd have done it. Therefore, I believe you're
being a tad unfair to the Pentium 4 design.
If you'd like to compare Pentium III to Athlon on a clock-for-clock
basis, I think it's a lot more reasonable, and for that comparison I
think Athlon is a more efficient engine. Of course, the Pentium III
design is about 2 years older, so that's what you'd expect, no?
I promise to shut up now, since this seems pretty off topic even to
me. :-)
-BobC
[EMAIL PROTECTED] wrote:
>
> Saying the code runs faster than on an "equivalent"
> Intel processor requires that we agree on what
> equivalent means, a discussion that I suspect won't
> benefit this email list. (Equivalent process
> technologies? Equivalent clock rates? Equivalent
> aggregate performance? Equivalent product intro dates?) -
I meant same clock frequency... :)
- Jussi Laako
