HowTo: Undervolt your notebook CPU for longer battery life

[Kiddion]

EDIT: I updated to the new kernel from the repo, but I don't have undervolting... huh? It is listed as installed, but I don't have PHC. I just downloaded all the available updates in Update Manager... do we need to do something else? I only have two kernel images in /boot, so I believe I am booting to the modified kernel when choosing 2.6.28.13... and 2.6.28.11 still works correctly. What's going on?

There was a problem for Centrino's (the depricated speedstep-centrino module was built-in and therefore used instead of the PHC acpi-cpufreq module). This should be solved in the latest 2.6.28.13-generic version 2.6.28-13.46~undervolt3.

[asuna]

First of all thanks for answering me.
It seems there is nothing to do. As you see in my previous post I've checked synaptics and the installed version is just the undervolt one.

cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
Always: no device

my menu.lst, I've posted it above, is the same as yours.

I've been following the steps to install the linux_phc module, and I got as far as ^anjie

I've downloaded and installed the 2.6.28-13.46~undervolt3 kernel from the PPA (via Update Manager), rebooted to it (although the grub menu says 2.6.28-13-generic), and I got this:

cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls : No such file or directory

I tried: cat: /sys/devices/system/cpu/cpu0: Is a directory

lsmod | grep acpi_cpufreq gives nothing (blank)

menu.lst looks normal, contains both 2.6.28-13-generic and 2.6.28-11-generic. Do I need to add the 2.6.28-13.46~undervolt3 entry to the list?

It seems as if I never installed the undervolt3 kernel, even though synaptics tells me its installed. Can anyone help?

I'm using an Intel Core 2 Duo T5500, dual boot with windows xp

[Schnitzelpudding]

No (automatic) fun here either.

Clean install of 9.04, updated everything (including kernel to 2.6.28-13), removed 2.6.28-11, added the PPA, ran Update Manager and let it install its stuff. This seems to have overwritten the original kernel, the acpi-cpufreq module exists but isn't loaded automatically ("CPU frequency scaling unsupported" popup after login and processor stuck at full speed). I've added it to /etc/modules and that seems to be working for now... is this supposed to happen? This is on a Core Duo (T2350) laptop, so nothing particularly exotic.

[Kiddion]

Did you add the acpi_cpufreq module to /etc/modules ? The modules isn't loaded automatically by the default Ubuntu startup scripts, as those suppose that the modules are built-in. If the /sys/devices/system/cpu/cpu0/cpufreq/ directory isn't there, the module has never been loaded.

[Shikaku2]

Oops, I don't know what I'm doing, ignore me.

[asuna]

Ok thanks for all the help

EDIT:
Finally got it to work!

After I downloaded and used PHC Tool

From http://linux.aldeby.org/linux-phc-cpu-undervolting.html

"There is no package, you have to download a subversion snapshot via:

sudo apt-get install subversion

svn co http://phctool.googlecode.com/svn/trunk/ phctool

The tool has a Analysis tab as you can see in the screenshot.

To get this to work, you first need to

sudo modprobe msr"

[adempewolff]

I hope this hasn't already been addressed in the thread. I tried looking for a while but did not see anything.

Nothing happens when I enter "lsmod | grep acpi_cpufreq". However I am using an Intel Core 2 Duo (which the howto states it has been tested with) and cannot figure out for the life of me why my kernal would be using a module for Centrino processors... (if it matters I'm also using 9.04, 2.6.28-13-generic)

Am I missing something here? Is there any other reason why I wouldn't get any output from that command?

[hegoburu]

Ok maybe someone could help me out here. I re compiled the kernel per phc forum instructions, installed phc-k8, rebooted. Lsmod gives me phc-k8 as loaded, checking scaling_driver in cpufreq reports phc-k8, however, there are no phc-specific files in the cpufreq directory. ?? Any ideas?

[Kiddion]

I hope this hasn't already been addressed in the thread. I tried looking for a while but did not see anything.
[...]
Am I missing something here? Is there any other reason why I wouldn't get any output from that command?

It was mentioned before, but you'll have to add a line containing "acpi-cpufreq" to /etc/modules

Ok maybe someone could help me out here. I re compiled the kernel per phc forum instructions, installed phc-k8, rebooted. Lsmod gives me phc-k8 as loaded, checking scaling_driver in cpufreq reports phc-k8, however, there are no phc-specific files in the cpufreq directory. ?? Any ideas?

Your processor isn't supported (yet). The current phc-k8 driver does not support undervolting for family 10h and family 11h processors (Phenoms and recent Turion X2 processors).

[mister_playboy]

There was a problem for Centrino's (the depricated speedstep-centrino module was built-in and therefore used instead of the PHC acpi-cpufreq module). This should be solved in the latest 2.6.28.13-generic version 2.6.28-13.46~undervolt3.

Hmm... I downloaded the newer version and it still doesn't work for me. My laptop is a Pentium dual-core.