[Mageia-dev] i686 must be Pentium II ?

[Thomas Backlund]

Giuseppe Ghibò skrev 26.9.2010 02:09:

> Not exactly. I'm not talking in just using -march=<something> but in
> also pushing -mfpmath=sse -msse (and maybe -msse2) , which should be
> much more than JUST 1-2% (1-2% is usually the benchmark
> tolerance)...

Well, here is a simple fact.

Yes, going for i686 + SSE2 would/could give some benefits,

BUT

It would close support for all theese:
- Intel i586 (all)
- Intel Pentium Pro
- Intel Pentium II
- Intel Pentium III (Including some Pentium D)
- 32-bit AMD Athlon
- AMD Geode
- VIA C3
- Transmeta Crusoe

So, thats not an option.


Now what about only i686 + SSE then?
It would still close support for all theese:
- Intel i586 (all)
- Some Intel Pentium D
- 32-bit AMD Athlon < XP/MP
- AMD Geode < NX
- VIA C3 (Samuel* and Ezra)
- Transmeta Crusoe

So, still not an option.


Now what about only i686 then?
It would still close support for all theese:
- Intel i586 (all)
- Some Intel Pentium D
- AMD Geode < NX
- VIA C3 (Samuel* and Ezra)
- Transmeta Crusoe

So, still not an option.


And then to point out some other facts:

Some of the benefits are already accounted for like you noted earlier:
"Of course we shouldn't forget that the MDV had already a system for 
providing optimized (look at /usr/lib/sse2 for instance) version of 
libraries according to instruction set supported."

And many applications capable of utilizing sse2 and other instruction 
sets already have runtime detection support, so no problem there.


So, where does that leave us?

Simple.
For 32bit installs, we will still support i586 as base.
For 64bit installs, it's simple as x86_64 is SSE2 by default.


Now, _if_ the Mageia community gets enough developers to think of _and_ 
support a "light netbook/legacy edition", then maybe we can think of 
doing a i586/i686 split, but for now we will use i586 as base.


And many of the users wanting i686/sse2 already have hardware capable of 
running x86_64, so that's what they should do, as there is where the 
future is.

--
Thomas