Re: [gentoo-user] USE="mmx mmxext sse sse2 ssse3 3dnow 3dnowext"

[Volker Armin Hemmann <volkerarmin@googlemail.com>]

On Dienstag 26 Mai 2009, Stroller wrote:
> On 26 May 2009, at 05:37, Volker Armin Hemmann wrote:
> > ...
> > If a package would build using say 3dnow without the cpu supporting
> > it it will
> > crash with an instruction error. So either it works always or never.
>
> Hmmmn.... so if I use it my applications might crash, but it's safe to
> use?
>
> The mplayer ebuild is stated to be "intelligent" about ignoring these
> flags if necessary, so I'm not sure that "if mplayer works, so will
> everything else" is a safe conclusion. My question was exactly if it
> was so - are other ebuilds also as "intelligent" as mplayer?
>
> > Just look at /proc/cpuinfo you find everything you need to know
> > there. It
> > isn't hard. In fact, it is really ,really simple.
>
> I'd disagree. If it were really simple, Portage would take care of it
> automagically for me. It (apparently?) doesn't.

portage does not take care. mplayers build has a cpu feature autodection.

Different stuff. Really.

>
> It's kinda a pain to have to look up what's supported on each system,
> and then edit make.conf accordingly. Especially as some translation is
> required: Adam Carter states, 'apparently "pni" = sse3'. What else
> might be this or that or something else? The suggested `grep flags /
> proc/cpuinfo` shows "apic sep mtrr" amongst others, but there appears
> no USE flags corresponding to those. Or are there?

apic is interrupt controller. mtrr is about ram access - and supported since 
pentium ... 1? mmx? 2? very early. There are no flags, because that stuff 
really is nothing apps care about (with the exception of X and mtrr - luckily 
for you, that is nothing YOU have to care about).


> Looks like `echo media-video/mplayer mmx mmxext sse sse2 ssse3 3dnow
> 3dnowext >> /etc/portage/package.use` unless someone else is able to
> be more informative.

yeah, except that is bullshit

no pentium can do 3dnow. Or was there a 3dnow flag in /proc/mtrr? No? Then 
don't even touch it. Same for ssse3. This has nothing to do with sse3. It is 
something completly different. And p4 never had this. 
Enable mmx, mmxext, sse, sse2 for everything and you are fine. Check for pni 
if you want sse3. Everything else is not for you.

look also here:
http://en.wikipedia.org/wiki/Pentium_4

as you can see:MMX, SSE, SSE2, SSE3 but sse3 only if you have 'pni' among your 
cpu's features.