[Beowulf] Thought that this might be of interest

[Joe Landman]

Vincent Diepeveen wrote:
> Impressive bandwidth.
> 
> Is this the so called 'k8h' revision which has improved SSE2 throughput?

As far as I know the k8h is a quad core (found by googling).  SSE 
throughput does appear to be better simply running a code that performed 
less well on a 275, but the performance difference (17.6%) was IMO 
indistinguishable from a clock speed delta (18.2%) to within the 
measurement error ... that is, if SSE2 does in fact run faster, I have 
not probed it yet.

Using the PGI and Intel compilers.  The latter appears to be doing its 
old tricks: I get

> landman at jackrabbit:~/URS$ ./xxxxxx.woodcrest
> 
> Fatal Error : This program was not built to run on the processor in your system.

Uh huh.

I took that string and googled it. 
http://www.devx.com/amd/Article/28001  If I had time I would no-op that 
test out and see how well it does.  The effort to do this is larger than 
I care to do.  Well, if anyone has a quick set of strings to look for, I 
really don't want to spend the time tracing the startup of the code.... 
  I can insert a few 0x90 by hand.

Its a shame as the late model Intel compilers generate reasonably good 
code.  Since they wish to do it only for Intel processors, and the world 
is decidedly mixed, this has implications on the use of Intel compilers 
for lots of people wishing to get the best performance on all platforms 
with a single compiler tool.  Doesn't it.

I thought they had fixed that in the 9.0 compilers.  Looks like I was wrong.

> 
> Mind running a prime95 test at 1 core and then at 4 cores, and print the 
> iteration time you can get,
> like you can find it here?
> 
> http://www.mersenne.org/bench.htm

Will pull it down, and see if I can get it going in under 10 minutes.

> 
> That's the time to do a multiplication and a modulo if i understand well 
> in order to try to win
> $100k : http://www.eff.org/awards/coop.php



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Joseph Landman, Ph.D
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