Changing the default 32-bit x86 arch for Fedora 12

[Steven M. Parrish]

> Way back when in February [1], FESCo decided that for Fedora 11, i586 would
> be the default architecture, and for Fedora 12, it would be some variant of
> i686. It's time to follow through on that action item.
>
> I've submitted https://fedoraproject.org/wiki/Features/F12X86Support. It
> defines the default arch as i686 + SSE2.
>
> Why?
>
> - Faster and more consistent FP math by using SSE2 registers
> - Allows for autovectorization by GCC where necessary
> - More clearly delineates our support set of targets, sticking true
>   to forwards innovation, not necessarily legacy support
>
> What CPUs do we lose that F11 supports?
>
> - Intel i586 (all)
> - Intel Pentium Pro
> - Intel Pentium II
> - Intel Pentium III
> - 32-bit AMD Athlon
> - AMD Geode
> - VIA C3
> - Transmeta Crusoe
>
> Does this lose the PAE/non-PAE kernel split?
>
> - Alas, no.
>
> Will a Fedora rebuilt in this manner work on ...
>
> - OLPC 1.0? No.
> - OLPC 1.5? Yes.
> - Atom? Yes.
>
> A seconday arch could be done for these older CPUs, if someone is
> interested enough.
>
> Comments? Flames? Predictions of doom?
>
> Bill
>
> [1] http://bpepple.fedorapeople.org/fesco/FESCo-2009-02-05.html

The OLPC folks have made a commitment use Fedora as the base for future 
releases for not only the XO-1.0 but for the new XO-1.5 which is still in 
development.  No we go and pull the rug out from under them by saying F12+ 
will not support the processor on the more than one million already deployed 
XOs.  Also over the past few months much of work has gone into packaging the 
Sugar Desktop and related activity packages for Fedora. 

I would instead propose that instead of killing off i586 that instead we make 
i686+SSE2 a new primary arch.  This will allow us to not only optimize Fedora 
for i686+SSE2 but still maintain a viable arch i586 for not only the XO-1.0 
but also for the many older but still usable machines that would otherwise be 
excluded from using Fedora. 

Steven