[ale] Motherboard ?

[Jeff Hubbs]

> Where this
> really is noticable is in multi-threaded applications. If you have a
> single threaded app, it won't run any faster than with one processor.
> However, the presense of an additional cpu will make your single
> threaded app seem more responsive because there will be another cpu to
> offload most of the system calls that your other cpu would 
> otherwise be
> forced to switch to. 

This is a good point.  Sometimes I'll have ktop up when I'm doing stuff and
there will be some things that I run that, through system calls, take up
"user" cycles and "system" cycles in roughly equal measure (at the expense
of nice cycles, which is of course my SETI at home getting intruded upon by
stuff I'm actually trying to do!)  For apps that work like that, yes, you'll
get a gain by having two CPUs chew on it. 

Just as a footnote, SETI at home is not multithreaded, but on an SMP machine
you can execute it more than once as long as you keep the data files
separated.  

I'm trying to plan out a rig of machines to run Rational LoadTest.  Rational
SiteLoad, the Web-based load-testing app that Rational provides for free (as
in beer), runs out of CPU on a PIII/667 w/ 512MB RAM at about 40 simulated
users.  I'm looking to make a rig that can run up to 1000 simulated users at
minimum cost, and I get the feeling that dualies are the way to go.
4-way-and-up boxes are of limited usefulness because simulated users also
take a lot of memory.

- Jeff
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