Re: Emulator, Inc

[Eric Smith <eric-no-spam-for-me@brouhaha.com>]

"Bryan Parkoff" <nospam@nospam.com> writes:
> I know that Pentium 4 has some problems, but I stay on Xeon Pentium III
> until Pentium 4 will be fixed.

I wrote:
> What problems are these?

Sheldon Simms <sheldonsimms@yahoo.com> writes:
> Cycle for cycle, It executes code a lot more slowly than a Pentium III,
> Athlon, or Athlon 64. That's all.

That's not a problem.  It was designed to do less per cycle but with a
higher clock rate.  That's a perfectly legitimate way to do processor
design, and was in fact how DEC made the highest performance microprocessor
in the world in 1991, the Alpha 21064.  It didn't do nearly as much in
one clock cycle as some contemporary processors did, but then, it didn't
need to.

> All that, however, it hardly matters since the Pentium 4 is capable
> of being run at much higher core frequencies, which makes up for the
> cycle for cycle disadvantage.

Yes, but that's a deliberate design tradeoff that Intel made.  It's not
like it was a screwup.

In computer architecture circles, the microarchitecture trends to greater
pipeline complexity vs. higher clock rate have been referred to as the
"Braniacs" vs. the "Speed Demons".  For instance, the R4000 series MIPS
processors were in the Braniac category, but the Alpha 21064 was in
the "Speed Demon" category.  Most processors in recent times have had
compromise positions somewhere inbetween.  For instance, the Alpha 21264
has out-of-order execution, but also didn't reach clock rates as high
as the Alpha 21164 when implemented with the same process geometry.  To
a first approximation, when you make the pipeline more complex, you
inherently raise the minimum cycle time.

Where Intel is in a bit of a pickle is with regard to marketing.  They've
been telling customers for years that MHz is the most important thing,
because their parts run at a higher clock rate, even though AMD's parts
actually can outperform Intel's when running at a lower clock rate.

But now Intel has the Pentium M, which does more per cycle at a slower
clock rate.  If they try to use their normal "more MHz is better"
marketing on that, customers will think it sucks, because its clock
rate seems slow.