[Motorola Droid RAZR] ice9tech:
To give everyone who wants to start over/underclocking there Razr's a head-start with some values, I think it would be best to gather some real-world data from the XDA community. You can drastically reduce your device's power consumption by undervolting, extending your battery life.

The data presented in this thread should be used as a general guideline, and will not be stable on all devices. At such a small die size (~45nm), imperfections in the semiconductor are unavoidable, and as such, each device will have a (slightly) different stability point. That being said, it's a lot easier to over/underclock properly when you have a set of known, working values on other devices (even acknowledging the fact that all CPUs have different stability points).

I personally have left my phone at stock speeds, but undervolted the CPU drastically to improve my battery life. For the technically inclined, power consumption of a CMOS circuit decreases quadratically as a function of voltage. So for the majority, halving the voltage of a CPU at the same frequency will reduce the power consumption to only one quarter of the original.

So, without further ado, here are my new set V_SEL values (as well as the stock, original ones). I manually tested the undervolted settings using the free StabilityTest application, which cycles through all clock frequencies in the table below, and ensures the CPU is stable at all frequency/voltage combinations.

Frequency | Stock | Undervolted
[MHz] | [V_SEL] | [V_SEL]
-------------------------------------
1200 | 61 | 45
1000 | 61 | 38
800 | 55 | 31
600 | 43 | 28
300 | 26 | 18***

(aside: does anyone know what units the V_SEL values are in?)

After the change, not only does the phone consume a lot less power (I can manage over 3 days on a single charge now, before it was around 2), it also gets less hot under use as well. Note that the values I got above do have some room for further adjustment, but they're very close to the minimum voltage values (the phone is very unstable when V_SEL = 40 at 1200 MHz).

*** Edit: You need to set the minimum voltage in the Calibration menu in QuickClock Advanced to set V_SEL lower than the stock value of 26 (thanks spikegibeault).

For those who are curious, you can manually set the V_SEL and clock speed values without using a tool by simply executing the following script (must be root, and should be done on every boot since the values revert to the default when the phone reboots).

echo 1 300000000 26 > /proc/overclock/mpu_opps
echo 2 600000000 28 > /proc/overclock/mpu_opps
echo 3 800000000 31 > /proc/overclock/mpu_opps
echo 4 1000000000 38 > /proc/overclock/mpu_opps
echo 5 1200000000 45 > /proc/overclock/mpu_opps
echo 0 1200000 > /proc/overclock/freq_table
echo 1 1000000 > /proc/overclock/freq_table
echo 2 800000 > /proc/overclock/freq_table
echo 3 600000 > /proc/overclock/freq_table
echo 4 300000 > /proc/overclock/freq_table
echo 1200000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
echo 300000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

Note that in the script above, I changed the minimum V_SEL to 26 so most people can just try the script after installing the kernel modules. To go lower than 26, you still need to use QuickClock Advanced to change the Calibration values. If anyone knows what value is modified in the system, please let me know so we can avoid having to use a discrete application (and thus, can simply use shell scripts to set all values).