On Dienstag 26 Mai 2009, Stroller wrote: > 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.
you can enable them globaly. 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. Just look at /proc/cpuinfo you find everything you need to know there. It isn't hard. In fact, it is really ,really simple.
