Opteron Vs. Athlon X2

[Lamont R. Peterson]

On Tuesday 06 December 2005 02:16am, John Haxby wrote:
> Robert L Cochran wrote:
> > I would like to keep to a budget of about USD $600-700 for a CPU
> > upgrade. I want to both develop and use open source software, which
> > means a lot of code-compile-test cycles. I want the compiles to finish
> > quickly. For example, PHP 6.0 (from snaps.php.net) takes about 4-5
> > minutes to compile on my single core Athlon 64 3500+, and I'd like to
> > cut the compile time in half. I also want to do web development with
> > PHP and databases. I want to be able to keep up with the current  CPUs
> > and get exposure to them.
>
> When you're compiling is your CPU running at 100% (near enough)?
> Chances are it is, in which case you should benefit from an extra CPU so
> long as you run either "make -j2" or "cc -pipe" (or both).  A while back
> when I had an two processor machine for development I found that "cc
> -pipe" ("make -j2" didn't work with the broken build system) cut
> compilation time dramatically and both CPUs were busy instead of just
> one of them.

Actually, I find that I get a little better performance for a single proc 
machine with make -j2 ... anywhere from 5-20%, depending.  On my dual Opteron 
box, I use -j3.

Here is my "rule-of-thumb" for computing the number to pass with the -j 
switch:  1 for each processor + 1 for each system + 1 if using a distributed 
build.

The thing is, the process of compiling several files requires more than just 
running the proc at full bore while compiling.  There are lulls in processor 
utilization.  These "valleys" (think of the looking at a scrolling processor 
utilization graph) get filled in by the "extra" process.  Usually, they don't 
all want to do I/O or some other non-processor-intensive activities at the 
same time, so most of the otherwise wasted clock cycles in the middle get put 
to good use.

Of course, this will mean a little more heat (if you could even measure it ?) 
during long builds.

> The other advantage of an dual CPU system, at least for software
> development, was that the autotests found several bugs that  we simply
> hadn't seen before -- every one of them some sort of race condition it
> was easy to trigger when you can have two processes running at the same
> time.

Gotta love it! :)
-- 
Lamont R. Peterson <lamont at gurulabs.com>
Senior Instructor
Guru Labs, L.C. [ http://www.GuruLabs.com/ ]
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