February 1997 brought yet another front-page mention of MMX, this time as the feature story. For those too young to remember from the first time around (most of you, probably), MMX was short for “MultiMedia eXtensions” and was a set of CPU instructions that made certain multimedia/gaming related tasks faster.
http://darth-azrael.tumblr.com/post/157328357746/tech-backissues-february-1998-brought-yet
boot’s cover story in February 1997 was MMX. MMX stood for “MultiMedia eXtensions” and consisted of 57 new instructions that were aimed at accelrating gaming and other multimedia functions. These were similar to (but not as powerful as) the Altivec instructions that came later with the PowerPC. At the end of the day, they were helpful but not earthshattering. They were first available in the 120, 150, 166, and 200 MHz Pentiums. If you were getting a new computer you definitely wanted the newer MMX version of the chips but by this time 3D accelerators were coming into their own and made a bigger difference than MMX. A few games did advertise themselves as being enhanced for MMX. A little later came the 233 MHz MMX Pentium and MMX instructions in various enhanced forms have been in Intel processors ever since.
https://steemit.com/retrocomputing/@darth-azrael/boot-february-1997