What do you guys thing about the P4

[Phillip D. Matz]

Hi,

> especially with a compiler that can use the SSE side
> of the microprocessor.

Which brings up another question.  My current impression was that SSE/SSE2
is only single-precision while G98 (and probably most computational
chemistry programs) requires double-precision -> if this is correct then SSE
doesn't help, rather, it invalidates ones G98 results.  Would anyone care to
set me straight?

Thanks,

Phillip Matz
matz at wsunix.wsu.edu

----- Original Message -----
From: "Richard Walsh" <rbw at networkcs.com>
To: <beowulf at beowulf.org>; <lindahl at conservativecomputer.com>
Sent: Friday, April 13, 2001 9:16 AM
Subject: Re: What do you guys thing about the P4


>
> All,
>
> I believe the arithmetic behind the 3.2 Gbyte/sec peak
> memory bandwidth in P4 system using PC800 RDRAM, and
> Intel's 850 (Tehama) chip set is as follows:
>
>       RDRAM memory speed        =   400 MHz
>       RDRAM channel width       =    x2 bytes
>       RDRAM "pumps" per cycle   =    x2
>       RDRAM channels on 850     =    x2
>       ---------------------------------------
>       Total On Board Bandwith   =  3200 MBytes/sec
>
>       P4 system bus speed       =   400 MHz
>       P4 system bus width       =     8 bytes
>       ---------------------------------------
>       Total On Chip Bandwith    =  3200 MBytes/sec
>
> (a single channel SDRAM system is  8*133=1.06 GBytes/sec)
>
> So P4/850 motherboards with PC800 RDRAM are well balanced.
> Problems with large linear systems, and cache and memory
> resonant reference patterns will keep the processor
> relatively busy and hide the RDRAM latency penalty
> which is about 2x that of SDRAM (the P4's faster clock
> also helps to reduce this penalty).
>
> I would expect G98 jobs run INCORE or DIRECTly with a
> large memory setting to show excellent performance
> especially with a compiler that can use the SSE side
> of the microprocessor.
>
> rbw
>
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