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Re: Features/ArchitectureSupport - changing what we build for



"Pentium Pro or better" is pretty reasonable. AFAICT, if I look really hard, the earliest PC I can buy around here is the first generation Pentium II (pre MMX). Most OSes do not support the i586 arch unless it's specifically geared towards older PCs or firewall distros. Linux mainstream distros seem to be unusually keen on remaining utterly backwards compatible as far as CPUs go. I personally think going that far back is unreasonable if it isn't explicitly stated in the goals of the project itself. For example, Damn Small Linux can remain arched at i386/i486, because its goal is to run on older machines as well as newer ones. Ubuntu or Fedora don't really have any business running on older machines, but Ubuntu is exempt because of their shared base with Xubuntu, which IS aimed for older machines. OpenSUSE Linux (how I despise thee *hisses*) runs primarily on i586 arch, with the exception of the kernel and a few other packages; however, in practice it doesn't run on a Pentium I. Honestly, I think Fedora needs to stop bottlenecking its performance by not optimizing its code for i586 or i686. I would prefer the code to be optimized to i686 when built as RPMs.

On Mon, Feb 2, 2009 at 1:17 PM, Gregory Maxwell <gmaxwell gmail com> wrote:
On Mon, Feb 2, 2009 at 2:03 PM, Jason L Tibbitts III <tibbs math uh edu> wrote:
>>>>>> "BN" == Bill Nottingham <notting redhat com> writes:
>
> BN> Please re-read.
>
> No need.
>
> BN> "the only statistics we have available".
>
> "are flawed".  Don't quote them at all if you know they aren't
> correct.  That's my only point here.
>
> BN> If you've got better ones, please share.
>
> You know I don't.  You also know that my not having any doesn't have
> any bearing at all on the fact that you shouldn't be quoting
> statistics you know to be incorrect.

With x86_64 (hopefully) covering the majority of the modern systems
what is the harm in leaving x86 i586 compatible?

Isn't the only difference in arch=i686 as far as userspace is
concerned cmov? It seems that some people question the general
usefulness of cmov:
http://ondioline.org/mail/cmov-a-bad-idea-on-out-of-order-cpus

"Pentium or better" is a nice understandable break point. "Pentium pro
or better" far less so. Fedora already has an offering for the high
end (x86_64; which also implies many other performance improving
differences)…


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