Changing the default 32-bit x86 arch for Fedora 12 (#2)

Bob Arendt rda at rincon.com
Thu Jun 18 04:45:31 UTC 2009


On 06/17/2009 03:00 PM, Richard W.M. Jones wrote:
> On Wed, Jun 17, 2009 at 01:52:26PM -0400, Bill Nottingham wrote:
>> - Build all packages for i686 (this requires cmov)
>
> This cuts out AMD Geode ...
>
> and for what ...
>
>>                P4 2.4Ghz       Athlon 3400+    Core2Duo E6850  Atom N270
>> march=i686/   -1.1%           +2.0%           +0.9%           +0.6%
>>   mtune=generic
>> march=i586/   +0.3%           -0.3%           -0.2%           +1.3%
>>   mtune=atom
>> march=i686/   -1.5%           +1.2%           +0.5%           +1.7%
>>   mtune=atom
>
> This just doesn't look worthwhile at all.
>
> My proposal is that we actually start to 'downgrade' x86, start
> compiling for baseline i386, and try to support people running Fedora
> on really old hardware, through projects like the Minimal Platform
> feature.
>
> Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones

Agreeing with Rich, what does this buy us?  Being generous, 1.7% means
you shaved 1 second off a 1 minute mp3 encode.  Perhaps measurement
accuracy is on the order of 0.5%?  And the P4 performance degrades;  Why
further cripple the slower chip?

This slight benefit doesn't seem worth the effort of re-doing the build
infrastructure and dropping/alienating older chip architectures.

-Bob Arendt




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