In my continuing quest to reduce PC power consumption, I'm researching underclocking and undervolting. Underclocking in linux is fairly simple as it is handled by the cpufreq modules. On the otherhand, it appears that CPU undervolting is only possible through BIOS changes of the FSB frequency and multiplier.
Here are some good links I've found so far:
List of undervoltable motherboards
Undervolting your AMD Powernow Notebook
Linux-PHC Patch for Pentium M CPUs
Gentoo Wiki Guide for Underclocking a Pentium M
Undervolting the AMD A64 X2 4200+ AM2 Processor
I just got lm-sensors installed on Debian, and I get this output:
w83627hf-isa-0290 Adapter: ISA adapter VCore 1: +1.41 V (min = +0.00 V, max = +4.08 V) VCore 2: +2.67 V (min = +0.00 V, max = +4.08 V) +3.3V: +3.31 V (min = +2.82 V, max = +3.79 V) +5V: +5.11 V (min = +5.08 V, max = +6.64 V) +12V: +11.92 V (min = +11.55 V, max = +15.20 V) -12V: -6.85 V (min = +5.40 V, max = +5.40 V) ALARM -5V: -3.84 V (min = +5.10 V, max = +3.44 V) ALARM V5SB: +5.56 V (min = +6.18 V, max = +6.83 V) ALARM VBat: +2.88 V (min = +3.47 V, max = +2.67 V) ALARM fan1: 1875 RPM (min = 332 RPM, div = 16) fan2: 5625 RPM (min = 332 RPM, div = 16) fan3: 0 RPM (min = 332 RPM, div = 16) ALARM temp1: +36?C (high = -1?C, hyst = -1?C) sensor = thermistor ALARM temp2: +27.0?C (high = +50?C, hyst = +45?C) sensor = diode temp3: +28.5?C (high = +50?C, hyst = +45?C) sensor = thermistor vid: +0.000 V (VRM Version 2.4) alarms: beep_enable: Sound alarm enabled
w83627hf info at lm-sensors.org
and:
Cool, this works:
echo "120" > /sys/bus/i2c/devices/9191-0290/pwm1
resulting in:
fan1: 2220 RPM (min = 332 RPM, div = 16)