Nuno Teixeira wrote: > > Hi, > > Just a little question: > > Does -march=k6-2 implies -m3dnow? Or -march=pentiumpro implies -mmmx? Pentium Pro doesn't support MMX; -march=pentiumpro (aka -march=i686) enables compiling with main i686 instruction set, no MMX\SSE or whatever.
> > I always thought that when I use -march it will enable other > porcessor specific optimizations like mmx and 3dnow (if available). No way. Besides, only a dozen of open-source UNIX applications can really profit from MMX, so it's absurd to use -mmmx for day-by-day use. To be correct, MMX is only useful for real-time video\audio processing. A little example: consider some 16-bit pixel set that you need to increase brightness, i.e. to add some value to every pixel. You can load a word into integer register, process, and store. You can also load a quadword of four 16-bit values into MMX register which is mapped onto FPU register, process them at once, and store. Indeed to be faster. Enabling MMX usually results in about 50% performance increase for true CISC processors like P-MMX, and about 20% for PII and up. --- Regards, Rhett __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
