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

[Stroller <stroller@stellar.eclipse.co.uk>]

Hi there,

I'm always rather reluctant to enable any of these, being unsure  
whether my ageing PentiumPro or Pentium 4 CPUs support such features  
as 3DNow! (originally an AMD technology) or the advanced SSSSSSSSSE3.

According to this page <http://en.gentoo-wiki.com/wiki/MPlayer>,  
however:

    You can greatly improve MPlayer's performances (in my experience, by
    up to +40%!) by recompiling it with appropriate CPU-related USE  
flags.

Moreover:

    Note: The mplayer build system will automatically detect your CPU
    settings if you allow it. Therefore, the safest thing to do is  
enable
    all of the optimization USE flags and let the script detect them. If
    you disable the use flags, then it will forcibly disable support for
    that optimization, and possibly break your build. In other words,  
add
    mmx mmxext sse sse2 ssse3 3dnow 3dnowext to your USE flags for this
    ebuild, and if your box supports it, it will work automatically.

w00t!

Should I enable all these USE flags globally? Will other packages also  
fallback safely as mplayer does?

Or should I add all these flags only to /etc/portage/package.use,  
allowing mplayer to make full use of the hardware USEs it supports,  
but limiting other apps to only those I'm really really confident  
about (i.e. "mmx" & that's about it).

Thanks in advance for all suggestions,

Stroller.