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

[Jon Ciesla]

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



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