Benchmarks: AMD64 vs i386 on Dual 246 Opteron

[Ken Gunderson]

On Fri, 29 Jul 2005 08:38:44 -0400
Martin Cracauer <cracauer at cons.org> wrote:

> ray at redshift.com wrote on Fri, Jul 29, 2005 at 02:32:34AM -0700: 
> > 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.
> > 
> > On the AMD64, I am pretty sure that I did *not* include the following lines like
> > I normally do on the i386:
> > 
> > options         SMP                     # Symmetric MultiProcessor Kernel
> > device          apic                    # I/O APIC
> 
> I occurse to me that not using one of the two CPUs might have
> something to do with a performance drop of approximately 50% :-)

Not to beat a dead horse here, but for the record, the numbers I
reported were definitely for a SMP kernel.

-- 
Best regards,

Ken Gunderson

Q: Because it reverses the logical flow of conversation.
A: Why is putting a reply at the top of the message frowned upon?