[Beowulf] 64bit comparisons

Bill Broadley bill at cse.ucdavis.edu
Fri May 14 11:48:21 PDT 2004

On Fri, May 14, 2004 at 09:44:01AM -0700, Robert B Heckendorn wrote:
> One of the options we are strongly considering for our next cluster is
> going with Apple X-servers.  There performance is purported to be good

Careful to benchmark both processors at the same time if that is your
intended usage pattern.  Are the dual-g5's shipping yet?  Last I heard
yield problems were resulting in only uniprocessor shipments.  My main
concern that despite the marketing blurb of 2 10GB/sec CPU interfaces
or similar that there is a shared 6.4 GB/sec memory bus.

> and their power consumption is small.

Has anyone measured a dual g5 xserv with a kill-a-watt or similar?

> Can people comment on any comparisons betwee Apple and (Athlon64
> or Opteron)?

Personally I've had problems, I need to spend more time resolving them,
things like:
*	Need to tweak /etc/rc to allow Mpich to use shared memory
*	Latency between two mpich processes on the same node is 10-20 times the 
    linux latency.  I've yet to try LAM.
*   Differences in semaphores requires a rewrite for some linux code I had
*   Difference in the IBM fortran compiler required a rewrite compared to code
    that ran on Intel's, portland group's, and GNU's fortran compiler.	

Given all that I'm still interested to see what the G5 is good at and under
what workloads the G5 wins perf/price or perf/watt.

Bill Broadley
Computational Science and Engineering
UC Davis

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