Probably you 'know' that Hyper Threading hurts the speed of chess engines as a lot of people say it's like that. In my opinion it's not always true. I use 6 cores (12 threads) processor and I made some tests using 4 popular strong chess programs: Deep Rybka 4, Deep Fritz 12, Critter 1.2 and Houdini 1.5a (which supports only 8 threads)
Each engine was tested in the same position for 30 seconds.
HT on:
Fritzmark: 43.6
Houdini 1.5a (8cpu) 14700 kn/s
Deep Rybka 4 (12cpu) 530 kn/s
Critter 1.2 (12 cpu) 12800 kn/s
Deep Fritz12 (12cpu) 21200 kn/s
HT off: all engines 6 cpus
Fritzmark: 35.37
Houdini 1.5a 15100 kn/s
Deep Rybka4 560 kn/s
Critter 1.2 12000 kn/s
Deep Fritz 12 17150 kn/s
As you can see Critter 1.2 and Deep Fritz 12 like HT, especially Fritz.
Deep Rybka 4 and Houdini 1.5a work better when HT is disabled, but notice if Houdini could use 12 threads it would be faster than on 6 cores.
The very important issue is system. I use Windows 7 Pro 64 bit and I read it is better optimized for HT than other systems. As I found - about 15% better than Vista.
If there is anybody who owns processor that can use HT I would be grateful for confirming that's what I said.
