Some CPU’s and system boards allow you to change operating voltage and frequency, resulting in a corresponding change in performance, and power consumed.
To test what frequencies are supported:
# kstat -m cpu_info -s supported_frequencies_Hz module: cpu_info instance: 0 name: cpu_info0 class: misc supported_frequencies_Hz 2000000000:2667000000module: cpu_info instance: 1 name: cpu_info1 class: misc supported_frequencies_Hz 2000000000:2667000000module: cpu_info instance: 2 name: cpu_info2 class: misc supported_frequencies_Hz 2000000000:2667000000 module: cpu_info instance: 3 name: cpu_info3 class: misc supported_frequencies_Hz 2000000000:2667000000
In this example (Xeon x5355), two frequencies are supported: 2.000 and 2.667 GHz
What is the current frequency:
# kstat -m cpu_info -s current_clock_Hz module: cpu_info instance: 0 name: cpu_info0 class: misc current_clock_Hz 2000000000module: cpu_info instance: 1 name: cpu_info1 class: misc current_clock_Hz 2000000000 module: cpu_info instance: 2 name: cpu_info2 class: misc current_clock_Hz 2667000000 module: cpu_info instance: 3 name: cpu_info3 class: misc current_clock_Hz 2667000000
In this example, two cores are running at 2.00GHz and two at 2.667GHz
To enable CPU power management add the following lines to /etc/power.conf and let pmconfig reread the config:
# vi /etc/power.conf ... cpupm enable cpu-threshold 1s ... # pmconfig #
Or download and install powertop. When you start it, press “p” to enable CPU power management.
Using dtpower:
To be able run dtpower as a superuser (only) edit /etc/default/power:
# vi /etc/default/power . . . PMCHANGEPERM=- CPRCHANGEPERM=- . . . #
ATTENTION: If you have an ASUS DSBF motherboard you need to upgrade the BIOS to AT LEAST version 1004. Older revisions do not support multiple frequencies.
Additional information: