Benchmarks: AMD64 vs i386 on Dual 246 Opteron

[ray at redshift.com]

At 07:35 PM 7/28/2005 -0400, Martin Cracauer wrote:
| > While this sounded like a long shot, I loaded FreeBSD 5.4 i386 on the machine
| > and after applying the exact same configuration to the OS, Apache, PHP and
| > MySQL, re-ran the benchmarks.  Much to my surprise, just changing the OS
from 64
| > bit to 32 bit caused the machine to double in speed.  The results are attached
| > in an Excel spreadsheet.  So the exact same machine, running the identical
| > configuration, performed roughly twice as fast when running FreeBSD 5.4 i386 vs
| > FreeBSD 5.4 AMD64.  Something about this seems so wrong to me :-)
| 
| I'm sorry but I cannot support these findings.  I don't have
| cut'n'paste numbers handy, but generally 64 bits speed up things quite
| a bit for me.  I have seen slowdown in 64 bit mode in e.g. bzip2 but
| generally there is a speedup.

Hi Martin - do you have any data to back up these statements?  If so, I'd like
to see it.

I will have another AMD Dual Opteron in here in a month or so and will do some
further benchmarks.  In going over my notes, the only thing I can see that might
have been a mistake was if I left out 'options SMP' from the AMD64 kernel config
file.  But I seem to recall you do not have to include that on AMD64 like you do
with i386 - can anyone confirm this?  I had to return the evaluation server, so
I can't test it this second.  As far as I call, the CPU's were launching
properly under both installations however.  

When I have our next AMD Dual Opteron machine in here, I will re-run the tests.

Ray