Re: fixed point vs floating point

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Tom says

<<Perhaps MMX is strictly Intel hype (no, I'd not an Intel employee or
  salesperson), but the general issue remains.  MMX is a way to speed up
  certain repetitive operations using SIMD parallelism.  But the
  opportunity for such parallelism must be recognized, either by the
  programmer, who codes in asm or calls an asm library routine, or by the
  compiler/optimizer.>>

I am beginning to get the idea that you have not actually looked at the MMX
instruction set in detail. I think you should, you would find that it is not
what you think it is!

<<The original reason to mention MMX in this thread, of course, was as
  an illustration that, though hardware designers may have been working
  in the last few years to optimize fpt performance, they have also
  started more recently to remember that some kinds of integer arithmetic
  are extremely important in a growing class of programs, and they've
  started to optimize integer performance.  The pendulum swings both ways.>>

There is nothing at all new about the MMX style of instructions. Such
instructions have been an integral part of graphics processors for a long
long time. Even the appearence of such instructions on a general purpose
microprocessor is not new, the i860 had similar instructions seven years
ago. These instructions are very specifically designed for certain graphics
operations, they are not some kind of general lets-make-things-run-faster
SIMD magic, which is the idea you seem to have. I really think you should
grab a copy of the MMX instruction manual and look at it!

There is no pendulum swinging here, except perhaps in the images generated by
the Intel PR machine and those who react to it without looking at details :-)