MMX

MMX is only used for Integer Operations I think. SSE is where you want to go for Floating Point stuff.

It is on those CPUs, and Athlons. Short for MultiMedia eXtensions.

It''s a form of SIMD processing, Single Instruction Multiple Data where one operation is performed on multiple pieces of data in parallel.

MMX in particular is integer only. Say you had 8 8bit integers in an array and you wanted to add the values of another 8 8bit integers stored in another array, you could do the whole operation with a single MMX instruction. Another example would be to perform alpha blending - you could do alpha blending on 4 16bit pixels at the same time.
It''s a lot more powerful than those simple examples, I''m keeping it simple to keep the post short, you can find tutorials all over the web.

More recently CPUs have had 3DNow! (AMD), and SSE (Intel, Streaming SIMD Extensions) which are also SIMD processing, but NOT MMX - they work with floating point values - so SSE and 3DNow! are very suitable for things like multiplying a list of vectors by a matrix etc.

--
Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com