Author: J. Wesley Cleveland
Date: 15:19:03 09/14/99
Go up one level in this thread
[snip] >>So, AMD's don't have a hardware BSF? Do you care about the hardware you compile >>Crafty on? I still use the table look-up without caring about the hardware. I >>should change.. >> >>Alessandro > > >AMD's _must_ have BSF/BSR. Because they claim to be Intel compatible, and >those instructions have been in all the pentiums... they have no choice. AMD's K6 have BSF/BSR, it just takes a number of cycles, so you don't gain much (if anything) using BSF/BSR. The old K5 had a 1 cycle BSF/BSR, so it probably would be a big gain. The Athlon docs say that BSF/BSR are slow instructions, but they don't say how slow. The original Pentium also had a slow BSF/BSR, so it was faster using the table lookup.
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