Author: Andrew Dados
Date: 10:12:10 05/08/00
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On May 08, 2000 at 05:45:29, 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. As you mentioned, all testing on those registers needs loading them to 'normal' registers, which complicates/slows down matters. I think using them for BB is not a good idea (findfirst,findlast - most common BB operations will get a huge slowdown), while using them for hash signatures can be done quite easily. Bad news is whole program will not speed up a lot.... -Andrew-
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