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Does AMD Cool n Quiet Slow Down Your System?

Does AMD Cool n Quiet Slow Down Your System?

I discovered today that having AMD Cool n Quiet enabled in my BIOS appears to be slowing down my Windows XP SP2 system by about 29% on memory & CPU intensive workloads.

Asked by: Guest | Views: 36
Total answers/comments: 2
Guest [Entry]

"After some fairly extensive testing I have concluded that CnQ definitely does significantly negatively impact the performance of my system.

With CnQ enabled, I consistently get between 1.8/3 and 2.2/3 of the performance against when it is disabled. This is for CPU & Memory intensive code, either single or multi-threaded, although the impact is greatest when there is a single thread maxed out.

The other point is that the performance I do get varies far more with CnQ enabled. With it disabled I get very consistent numbers.

EDIT 2010-05-24: After a driver update from AMD CnQ no longer has a negative performance impact. But it still seems to cause system instability, although not as frequently as previously - every few days instead of consistently within 24 hours. A manual crash-dump generated when the system stopped responding revealed all CPU cores to be executing within the AMD CPU driver, so no real luck there except to implicate CnQ without definite proof.

EDIT 2011-02-11: After upgrading from Win XP to Win 7 the identical hardware is no longer having stability problems with CnQ and all power management functions seem to be working exactly as expected. Esp. hybrid sleep and resume are significantly improved; I love having a 3 second resume for a desktop from S3 sleep, with the disk image recorded in case of abrupt power loss."
Guest [Entry]

"http://support.microsoft.com/kb/896256

Check the PerfEnablePackageIdle registry setting.
On dual core systems (e.g. my Athlon64 X2 4000+) this should have value 1.

I don't know which processor drivers or Windows updates control this setting, but i've seen systems with value 0 which will jump CPU frequency while executing a 100% single threaded task (e.g. SuperPI).

So with value 0 you won't get maximum performance with Cool n Quiet on."