amd64 slower than i386 on identical AMD 64 system?

Bill Moran wmoran at
Tue Mar 14 16:26:26 UTC 2006

On Tue, 14 Mar 2006 17:10:12 +0100
Alexander Konovalenko <kono at> wrote:

> I am just trying to understand, the conclusion is that all people who got i386 
> benchmark better than amd64 one, on the same X2 hardware, were running not 
> SMP kernel on amd64 and never bothered them self to build and use a proper 
> kernel for their platform? Naively I thought that problem is much 
> serious... :-P

We've been doing some tests here (on Dell Poweredge 2850) and haven't
done extensive tweaking (have tried different -O or any other compile

So far, our conclusion is that running amd64 binaries on an amd64
kernel is slower than ia32 binaries on an ia32 kernel.  We're
comparing identical 2850 hardware, both kernels built with SMP
(although there seem to be some issues related to running SMP on

We've been using ubench and pgbench (since these will be PostgreSQL
servers) to test.  We're seeing that the 64b stuff runs just a bit
slower.  We're also seeing that the amd64 doesn't seem to scale up
to using more than one processor, but that's an issue under investigation
(see other thread on this list)

These are not conclusive tests at this point, but it's more data for

Bill Moran
Collaborative Fusion Inc.

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