Author: Dominic C. Marcello
Date: 03:30:56 09/19/01
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As far as the penalty for using 64 bit bitboards on a 32 bit machine, with intel's mmx registers on the Pent pro and later, the penalty can almost disappear with a little inline assembly. Some instructions are not avallable for use with the mmx registers though. For instand, bsr and bsf ( bit scan reverse and forward) have no mmx instruction equivalent, but there is an mmx equivalent for and, nand, or, xor (but not not), as well as left and right shifts. It's a lot faster than treating the bitboard as two seperate double words, and if intel would just add a bit scanning function to it, bitboards could be operated on exclusively in the mmx registers. There's also some newer instructions on the pent IV, one of which would allow you to extract an 8 bit rank from a 64 byte board.
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