There is a fix for a performance issue with Windows XP and Amd Athlon64 X2 cpu's that have come out recently.
Issue
Quote:
If you run Windows XP on a computer that has multiple processors, single-threaded workloads may move across available CPUs. This migration behavior is a natural artifact of how Windows schedules work across available CPU resources. However, if a computer is running with the Adaptive processor throttling policy, this thread migration may cause problems. For example, the Windows kernel power manager may not be able to correctly calculate the optimal target performance state for the processor. This problem occurs because the individual logical or physical processor core may appear to be less busy than the processor package actually is. On performance benchmarks that use single-threaded workloads, this artifact may become evident in the following ways:
• Decreased performance
• A high degree of variance between successive runs of the same benchmark tests
In English. If you single thread program (most are) gets sent to the other cpu and the other cpu is in low power mode (runs slower to save power), it doesn't wake up and run at normal speed.
the file name for the hotfix is WindowsXP-KB896256-v3-x86-ENU.exe
You will have to find it on the net or call ms for free to get this file.
OR
Disable Quiet N Cool - in Control Panel, Power Management turn of aka Power Scheme = Always on. This will disable any energy features.
I would also do the following:
Check for any mother board bios updates in regards to amd's Quite N Cool technology.
This is one of those odd issues that some people have not noticed it all, people have noticed gaming benchmarks improvements with systems with dual core's go up.