Subject: Building one's own cluster and 4 gig MB's

From: Avijit Ghosh <[email-masked]>
Date: Wed, 5 Jan 2000 22:01:41 -0500 (EST)

Dear CCL Members,

	We are currently considering buying a cluster of machines
for || MPI work, as well as a four gig box using the ungodly expensive AMI
Megaplex mother board. My question in particular is how are people's
experiences using the AMI motherboard w/ both solaris and/or linux (w/ the
current set of patches) at 4 gigs. Are there are any obvious 
incompatibilities that we should be concerned with. (I've been assured
that there are stable bigmem patches floating around somewhere).

	Also, in a fit of madness we are somewhat hesitantly considering
getting dual celeron (500mhz) boxes rather than dual PIII's (The celerons
would be sitting on the same mb and would have 100 mhz ram etc
(allegedly). The tradeoff would be only perhaps then the 128k full speed
cache v 512k 1/2 speed cache and the specfp ratings of the celeron v
pIII doesn't look so bad. Needless to say, most people don't build
clusters w/ celeron boxes but the pricing ($1100 v $1400 w/ 256 megs)
seems good enough to at least consider before chalking it off as a bit of
delirium caused by too much alcohol. In any case, any bits of wisdom,
advice and such would be very much appreciated.

	-Thanks much,
	Dr. Avi Ghosh

---

From: "Brian D. Haymore" <[email-masked]>
Date: Thu, 6 Jan 2000 00:24:22 -0700 (MST)

I would shy away from quad processor boxes due to the limited memory
bandwidth in current SMP intel systems.  Any use of this type of system
that requires memory bandwidth will pay a high penalty.  If your specific
needs do not, then by all means go for it.  A PIII 600 sees around 400MB/s
average memory bandwidth with PC-100 memory based on the "streams" tests.
Now if you have  a quad processor you get 1/4 of 400 per proc which is
pathetic.

Celerons do an ok job, but our testings have shown that in caculations
like Gaussian the cache does kill the performance in comparison to
PII/PIII systems.  Note, I've not tested with the new coppermine PIII
processors that have 256K of full speed cache.  Pluss if you use current
compilers, probably comercial, you can see some speed benifit of the new
SSE instruction set of the PIII that isn't to be hand in the current
celeron processor.

To step away from that whole idea I'd propose the AMD K7/Athlon processor.
Whe have found in our tests it to performe 20-80% faster then the same Mhz
Intel processor.  That said you can now dedicate a single memory bus to
each processor and in many cases get near dual intel processor performance
with a single processor.

You might want to check with your hardware vendor of choice to see if you
can "Demo" hardware that you might like to buy before buying it to test it
accourding to your needs.  It was in doing just thist that I did my first
tests on the Athlon processor.  Since then we have been quite exclusive in
buying Athlons due to there performance and stability. 

--
Brian D. Haymore
University of Utah
Center for High Performance Computing
155 South 1452 East RM 405
Salt Lake City, Ut 84112-0190

Email: [email-masked] - Phone: (801) 585-1755 - Fax: (801) 585-5366

On Wed, 5 Jan 2000 [email-masked] wrote:

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