AMD Cool n Quiet
Before moving onto the actual tests, we have a few words regarding Linux and AMD Cool 'n' Quiet/PowerNow. First off, information pertaining to a specific CPU can be attained from sys/devices/system/cpu/cpu0/cpufreq. The available items are affected_cpus, cpuinfo_cur_freq, cpuinfo_max_freq, cpuinfo_min_freq, scaling_available_frequencies, scaling_available_governors, scaling_cur_freq, scaling_driver, scaling_governor, scaling_max_freq, scaling_min_freq, and scaling_setspeed. Contained inside of cpufreq/scaling_available_frequencies are the various frequency levels/states at which Cool 'n' Quiet supports. The specific voltage levels that correlate to the frequencies are not listed. In the event of using an AMD Athlon 64 3000+, only 2 states were available -- 1800MHz and 1000MHz.
Additionally, more information can be attained from cpufreq-info. This program developed by Dominik Brodowski displays the driver used, hardware limits, available frequency steps, available cpufreq governors, current policy, and current CPU frequency.
Finally, proc/cpuinfo displays general CPU information that we continually use at Phoronix such as the vendor_id, model, model name, stepping, CPU frequency, cache size, flags, bogomips, address size, and power management.