What lessons did Intel’s MMX and AMD’s 3DNow! extensions teach us about ISAs?

Question

What will be an ideal response?

Answer 1

The slogan of the RISC and post?RISC computer designer, or Amdahlista, is “Make the common case faster”.
Early RISC architectures were the first to throw away complex instructions. The Motorola 68K family (now the
Freescale ColdFire family) carried CISC complexity to extremes in the 68020, with memory indirect addressing
and remarkably complex bit field instructions. Motorola then removed some of the complex instructions from
the instruction set of later processors like the 68060. Such complex operations proved cost?ineffective.

However, the addition of SIMD short vector operations to the ISAs of many processors changed the direction of
computer architecture. Why? Because what was once the uncommon case had now become the common case.
First? and second?generation processors were never intended for multimedia applications. They were too slow,
main store memory was too expensive, and hard drives lacked the capacity to store lots of high definition
images and video. Today, all that has changed and even humble battery?powered, hand?held devices can
handle multimedia. Consequently, SIMD operations are now necessary to handle the simple, but highly
repetitive, operations of multimedia.

What is the lesson? It’s still “Make the common case faster,” but perhaps it’s now “Make today’s common case
faster, but keep an eye on what the common case will become tomorrow.”