Author: Bo Persson
Date: 06:49:03 05/13/00
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About a week ago, Bas Hamstra wrote: >What are the experiences about using the MMX registers for 64 bits manipulations >so far? > >There are 8 64-bits registers just sitting there, doing nothing! They can do >OR/XOR/AND like normal registers, in 1 tick. common instructions are pairable, >so 0,5 tick. They are supposed to load/unload as fast as normal registers. >Everything one needs, you would think. > >I have done some experiments, and got them to work fine. One problem I see is >that they don't set the flag register. For example: how do you test if a >bitboard is zero? Secondly it doesn't seem as fast as I hoped, but that could >also be my lack of asm experience. > >Anyone other experiences? According to "the book" it should be fast. So why >isn't anyone using it? EIGHT mighty registers!! > > >Regards, >Bas Hamstra. And the only three answers so far seem to be: "Bad news is whole program will not speed up a lot...." "I sounds like a good idea, but..." "IMO, you would have to pay a high price for it." Even though I tend to agree with these posters, I also really *would* like to find something useful in MMX. Except as a basis for Intel marketing hype, of course... Anyone?? Please... Bo Persson bop@malmo.mail.telia.com
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