Re: RFC: [2.6 patch] better i386 CPU selection

[Robert Schwebel <robert@schwebel.de>]

On Sun, Sep 07, 2003 at 01:28:13PM +0200, Adrian Bunk wrote:
> The patch below tries to implement a better i386 CPU selection.

Did you look at how rmk does CPU selection in the ARM tree? He has
developed a very sophisticated scheme as there are lots of completely
different cpu implementations, using a few cores. It might be an idea to
make the schemes more uniform than they are now. 

> There are two different needs:
> 1. the installation kernel of a distribution should support all CPUs 
>    this distribution supports (perhaps starting with the 386)

Ack. 

> 2. a sysadmin might e.g. want a kernel that support both a Pentium-III
>    and a Pentium 4, but doesn't need to support a 386

Ack. 

3. Embedded forlks might want to make a kernel which has support for
exactly the used processor and nothing more. 

> Changes:
[...]
> - AMD Elan is a different subarch, you can't configure a kernel that 
>   runs on both the AMD Elan and other i386 CPUs

Ack. Same with for example Geode. And the subarchs might have different
implementations, like Elan SC400, Elan SC410, Elan SC520. 

> - @Robert:
>   there were no Elan CFLAGS in arch/i386/Makefile???

That seems to have evolved since I last touched the Elan stuff. The
Elans are more or less 486 cores with some edges, so adding -march=i486
should be ok. 

> - which CPUs exactly need X86_ALIGNMENT_16?

I've just copied that from 486. 

> A 2.6.0-test4-mm5 kernel with this patch applied compiled and bootet on
> my PC.

I could do some tests on an Elan board, but not earlier than end of next
week as I'm out of office for some days...

Robert
-- 
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