[RC5] P4 Speed Question

Ryan Malayter rmalayter at bai.org
Wed Jun 13 18:30:30 EDT 2001


www.news.com reports a forthcoming DDR chipset from Intel for the P4, code
named "Brookdale," Expected "early next year."

But as you say, so the f*ck what... P4 performance sucks with P3-optimized
code. But the P4 isn't all that bad of a CPU core... it's just a bad choice
for the current Windows software market.

The SPEC CPU2000 bechmarks, which are designed to resist hand-tuning, but
allow for compiler instruction-order optimizations, show us some of the P4
core's potential. (I know that there are still loopholes in SPEC's hand- or
feedback- optimization rules. Manufacturers can exploit these to a degree,
but CPU2000 is much stricter than CPU95 in this regard, and a new enough
benchmark that Intel/AMD probably haven't had time to really juice up their
compilers with CPU2000-specific optimizations. In any case, benchmarks like
SPEC are really the only way to compare two different CPU architectures
equitably).

						Cint200	Cfp2000
Athalon 1.4/PC2100 DDR SDRAM		554		458
Intel P4 1.4 Ghz/PC800 RDRAM		529		538

As you can see, the P4 core fares well running P4-optimized code
clock-for-clock with the Athalon. (AMD chose to use Intel's p3-optimized 5.0
compilers, Intel used the same compiler with P4 flags set). These benchmarks
were submitted by AMD and Intel themselves to SPEC, so you can bet they
represent the best both companies could muster for their platforms.

Still, since most binary code today is P3-optimized, and the Athalon is
designed for this code base, that's what I'd buy next week. But if/when MS
and other vendors start optimizing instruction order for the P4, you're
going to see the Athalon's current application-level speed advantage
disappear. Intel is still, after all, the bully in the market, and they're
going to make P4 optimization pretty cheap and for most x86 shrink-wrap
developers.

Somewhat ironically, it's the Linux folks - who can recompile most of their
software to their liking - that might find they actually like performance
(maybe not price) of the P4 right now. Assuming, of course, that these Lunix
folks have access to good P4-optimized compilers and script interpreters...

	-ryan-


-----Original Message-----
From: Andrzej Hamka³o [mailto:niktu at dcc.pl]
Sent: Wednesday, June 13, 2001 12:00 PM
To: rc5 at lists.distributed.net
Subject: RE: [RC5] P4 Speed Question


> It is, the nForce chipset from nvidia introduces dual DDR sdram banks with
> a combined bandwidth of more then the dual channel rdram that intel is
> pushing for the p4 and with much lower latency.
>
> On Wed, 13 Jun 2001, dan the person wrote:
>
> > Peter Cordes wrote:
> >
> > > On Tue, Jun 12, 2001 at 12:31:49AM +1200, dan the person wrote:
> > > > Only thing super about a p4 is it's super high price.
> > >
> > >  In their defence, they do have more memory bandwidth than
> > > any other PC
> > > hardware, with dual rambus channels feeding a 400MHz bus.
> > >
> >
> > Is this not more a feature of the motherboard chipset than the
> CPU design?

Well, time to spam out of list subject a bit ....

Processor-memory bandwith depends on motherboard (chipset, type of ram)
or processor (type of processor bus)
- every time you get LOWER value of both, slower componnent chokes other ...
(extra ram bandwith could be used ie. by graphic pocessor, or in propely
designed
dual system - Intel designs do not apply, there all procs share same bus
...)

Latencies (of memory, chipset and proccesor bus are additive - and
bigger latency is bad, FYI ;)


and now short look back:
<SLB>
RDRAM (big latency, big bandwith) +
first incarnation Pentium III (100Mhz single pumed bus - rather slooow,
even newer 133 version don't catch up even close with RDRAM)
=
what you get?
you right!, weak points of both (big latency, low bandwith system)
- but you are proud owner of most expensive system in shop :))))))
- congrats to INTEL for that ingenious idea
</SLB>

and now present:
best of best list:
DDR RAM - highest badwith, lowest latency, sane price
nForce chipset - make that bandwith twice :), one but:
you can use it up for bulitin geforce MX ...

P4 100*4 bus - nice thingie, but besides bus there are other thingie
in processor to watch not to screw up ...

AMD's fastest Proc bus is 133*2
(if only AMD would launch 266*2 procs :)

For accuracy: I know, width of bus are important too (took that under
consideration, thats why i won't say that RDRAM's  are fastest :)


<rant>

But Mhz are THE MOST IMPORTANT, right?
Then people buy 1,7GHz P4 system and are suprised ...

I bet, the same money could buy you dual Athlon DDR system ...
(if not 1,4Ghz kind, certainly 1,33, but considering prices of RDRAM,
and i850 motherboard i think you could even save on dual 1,4Ghz  :)
you would be suprised, this time rather positively ...

Most people don't get it that even single 1,4Ghz Athlon performs better than
1,7GHz P4 ...
especially on code unoptimized for P4 (currently? - about 98%)

Then, most programs that ARE optimized for P4, (or for some strange reason,
run better :) can take advantage of second processor (2 in price of 1,
remember?)

I will not compare cow speed on these systems ... (quick guess: 4:1 in favor
AMD,
somebodybdy check that and precise it out), because rarely somebody buys
system only to run dnetc.

I can't think of application that would justify P4 existance in current form
...
      ... then again you could run Quake III under win ME  :)))  (scratch
one Athlon :))))

Now you know why Intel launched 1,3GHz cheepo P4. If somebody wants
develop and optimize his apps for P4, you can't force poor guy to waste too
much
money :)


</rant>

Always wanted to write that:
Dear Intel, please make good motherboard chipset at last (DDR?, hoping), if
Via won't have good
concurency, they won't improve their chipsets as much... (that nasty latency
thing ...)
BX owner



PS. I didn't bored you to death?, did you really read all of this?, wow :)

PPS. excuse my keyboard, it sometimes can't spell propely ;) and
excuse me for being blunt, just got fed up with today exam, and had to let
off steam ...

PPPS. Weird, all my essays always came out shorther than this ...

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