64-bit vs. 32-bit Computing

There's no doubt that for certain applications the
increased address space provided by a 64-bit computer
is a good thing. But, there aren't that many of these
applications.

Now that the new 64-bit Intel Core Duo/Solo processors are
out, and now that new AMD Athlons are all 64-bit, I'm
wondering when and why people are running them in
64-bit mode other than for database applications.

I just did a quick test on a new Dell server with a Core Duo
and 1GB of RAM. I loaded Fedora Core 5 in 32-bit mode and
timed a build of a fairly big app (subversion). I then loaded
Fedora Core 5 in 64-bit mode on the same PC, and timed the
same build. I think this is a reasonable test since
it does a lot of both I/O and computation. The results weren't
what I expected.

It turned out that the build took 2 minutes of elapsed time
in both cases. However, the 64-bit build took 12 seconds less
of usermode time, and 12 seconds more of system time. Go
figure.

--
Jon Forrest
forrest@ce.berkeley.edu
Computer Resources Manager
Civil and Environmental Engineering Dept.
305 Davis Hall
Univ. of Calif., Berkeley
Berkeley, CA 94720-1710
510-642-0904
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