Re: Which 32 bit kernel runs better under AMD64 architure, 686 or k7?

On Wed, Aug 30, 2006 at 03:27:34AM -0500, Ron Johnson wrote:
Roberto C. Sanchez wrote:
On Tue, Aug 29, 2006 at 11:33:14PM -0300, Marcello Di Marino Azevedo wrote:
Probably you are tired to see tons of questions like this, but...

I have two new servers coming for a critical mission application. My
question is simple, will sarge i386 port (32 bit only) runs fine under
an AMD64 X2?

For example, if I install kernel 2.6.8-k7-smp it will see 2 CPUs?

Which 32 bit kernel runs better under AMD64 architure, 686 or k7?

Well, the 686 kernel is for 686 CPUs (which the amd64 is not).

All K7 CPUs most emphatically *are* 686 CPUs, since they execute all
the relevant Pentium Pro opcodes.

Also,
the k7 kernel is for 32 bit Athlon CPUs (which the amd64 is not).

The K8 (in 32-bit mode) most assuredly *is* a K7. (What, you think
AMD would break backward compatibility? That's the big draw of AMD64.)

So, the AMD64 (in 32-bit mode) is a K7, and the K7 "is" 686, either
kernel will work.

You
need a k8 kernel, specifically. Of course, if you run a kernel with SMP
enabled, and you have more than one processor, you will see more than
one processer.

This is correct. You need an SMP-enabled kernel.

To get a 0.5% speed boost, use a k7-SMP kernel.

Correct on all counts. However, what is the point of having an amd64
CPU to then run an "inferior" kernel on it? I was not concerned with
the question of compatibility, which you adressed, but rather which is
the "best" kernel for that CPU.

Regards,

-Roberto

--
Roberto C. Sanchez
http://familiasanchez.net/~roberto

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