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How Well Is AMD CnQ Working For You On Linux?
Last week in Prague I heard from a Linux developer who was saying AMD Cool 'n' Quiet was no longer working out too well on his AMD-based systems. CnQ, of course, is the AMD technology for dynamically lowering the clock frequencies and voltage when the processor isn't under load in order to lower the power consumption and heat output -- AMD's equivalent to Enhanced Intel SpeedStep Technology (EIST).
Last year when testing the AMD FX-8150 was the last time I explicitly looked at the AMD Cool 'n' Quiet performance under Linux. In concluding that article I wrote, "Cool 'n' Quiet is good for dropping the CPU clock speeds and voltage when idling or with minimal load, which lower the operating temperature and system power consumption. When the FX-8150 is being stressed, having Cool 'n' Quiet enabled was not detrimental to the system's performance."
I've also tested Cool 'n' Quiet in previous years to find similar results that it was useful for reducing the power consumption by a small but measurable amount when the CPU is under minimal load; this technology has been found in AMD CPUs going back to the Athlon 64 days.
After hearing that Cool 'n' Quiet is now less beneficial under Linux, I'm going through on some different AMD hardware to see if it has indeed regressed or is some more isolated problem specific to only some CPUs/motherboards/BIOS. So far I did run a few tests from the brand new AMD FX-8350 Vishera with its eight Piledriver-based cores when toggling Cool 'n' Quiet support from the ASUS Crosshair V Formula motherboard. The results in this article is not only to be on the look-out for problems but also to see how well the latest-generation AMD hardware is performing power-wise with CnQ support.
If you're using AMD hardware for some time, have you noticed any changes in the power consumption potentially concerning Cool 'n' Quiet technology?