interesting... I have a dual xeon 3.6Ghz (nocona) server running 32bit Win2003
Server... fired up two copies of prime95 on it....
Now, these cpus are 'hyperthreaded' so windows shows 4 CPUs, 0-3... I
naturally wanted to use CPU affinity to run one copy on each PHYSICAL cpu...
I guessed that cpu[0,1] would be the two threads of the first physical CPU
and cpu[2,3] would be the two threads of the 2nd CPU, so I set affinity of the
two instances to 0 & 2 respectively... I was getting around 0.070
secs/iteration on one of these, which was hardly faster than my 2.5Ghz home
system, WTF? So I reset affinity to 0 and 1, and voila, now I'm getting
0.044-0.047 which is MUCH more like it. with only one prime95 running, its
0.040 (these are 29,400,000 range M numbers)
so it appears cpu0 & cpu2 are the same physical CPU, as are 1 & 3, at least in
win2003 server.
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