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Re: F12 to require "i686", but which CPUs do not qualify?



Tony Nelson wrote:
I've noticed that F12 will require a CPU with "i686" architecture, and that my Athlon 1.2GHz won't qualify. I accept that F11 is the last Fedora release that I'll be able to use. My concern is that many present Fedora users will be unpleasantly surprised that a new installation doesn't work, or at least that they've wasted the download.

The Release Notes, starting with the F12 Alpha Release Notes, should tell users about this, and so should the release announcements. The difficulty is in telling them what exactly is an "i686" CPU, as that is defined by GCC and is said to be a moving target (over the years). I'm hoping that someone qualified can make the appropriate changes to the Releases Notes wiki (I don't know what all the requirements are, though I do know that the Athlon does not support SSE/SSE2).

Is there a simple way for ordinary users to know if their CPU is expected to work on F12 (as an "i686" according to GCC)? Is there a tool to run that doesn't require downloading F12?

Quoting Bill Nottingham:

Given the loud feedback, I've updated the proposal at:
	https://fedoraproject.org/wiki/Features/F12X86Support

The revised proposal:

- Build all packages for i686 (this requires cmov)
- Optimize for Atom

Why?

- We don't really support i586 in any meaningful matter
- OLPC still works with base i686
- We are likely doing a mass rebuild for F-12 anyways, might as well switch
 while we're doing it
- Atom is the only currently produced 32-bit x86 chip of note; optimize
 for what's currently available

If you want numbers, I did some benchmarking of code [1] with various
build options on a variety of processors, with the F-11 gcc code. All
of these results are relative to a F-11 baseline of "-march=i586
-mtune=generic".

		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

Bill

[1] gzip, bzip2, math simulation, mp3 encode/decode, ogg encode/decode



--
in your fear, seek only peace
in your fear, seek only love

-d. bowie


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