Cool'n'Quiet

Cool'n'Quiet is a CPU speed throttling and power saving technology introduced by AMD with its Athlon 64 processor line. It works by reducing the processor's clock rate and voltage when the processor is idle. The aim of this technology is to reduce overall power consumption and lower heat generation, allowing for slower (thus quieter) cooling fan operation. The objectives of cooler and quieter result in the name Cool'n'Quiet. The technology is similar to Intel's SpeedStep and AMD's own PowerNow!, which were developed with the aim of increasing laptop battery life by reducing power consumption.

Due to their different usage, Cool'n'Quiet refers to desktop and server chips, while PowerNow! is used for mobile chips; the technologies are similar but not identical. This technology was also introduced on "e-stepping" Opterons, however it is called Optimized Power Management, which is essentially a re-tooled Cool'n'Quiet scheme designed to work with registered memory.

Cool'n'Quiet is fully supported in Linux from 2.6.18 (using the powernow-k8 driver) and FreeBSD from 6.0-CURRENT onward.