Undervolting a Pentium M 2GHz

For anyone working on undervolting their CPU, I’m posting the voltage table for my Pentium M (before and after) for its supported voltages.

New voltage table (Clockspeed/Voltage):

800000Hz/700mV (800MHz)
1067000Hz/798mV (1.07GHz)
1333000Hz/894mV (1.33GHz)
1600000Hz/982mV (1.60GHz)
2000000Hz/1116mV (2GHz)

The original table was (Clockspeed/Voltage):

800000Hz/988mV (800MHz)
1067000Hz/1068mV (1.07GHz)
1333000Hz/1132mV (1.33GHz)
1600000Hz/1212mV (1.60GHz)
2000000Hz/1308mV (2GHz)

As you can see, this caused a drop of nearly 200mV, allowing the computer to run in 2GHz with the same amount of energy it originally used for 1.33GHz. That’s like a free 700MHz of speed with zero electricity cost.

Now do you see why it’s so important to undervolt?

To confirm which processor I have, here is the value of /proc/cpuinfo:

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 13
model name : Intel(R) Pentium(R) M processor 2.00GHz
stepping : 8
cpu MHz : 800.000
cache size : 2048 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx up est tm2
bogomips : 1598.10
clflush size : 64