HowTo: Undervolt your notebook CPU for longer battery life

[sullust]

hi all,

I installed this patch and got my new values. I edited the rc.local file, and put the new voltage pairs in. But now, after i reboot, the system starts up but my screen goes black right before xserver starts and prompts me for a login.

I think it may be caused by the speedstep-centrino module I see, but I am not sure how to blacklist it. Has anyone else seem this?

How do I blacklist the centrino module?

[sullust]

Apparently it wasn't the speedstep-centrino module. The optimize script just set my values too low.

I ran into the same issue as Arthur, in that the first time I ran the optimize script, the steps counted all the way down to zero, then lock when the script exited.

I reset the script and executed it until the end. The results:
Before: 12:44 10:36 8:28 6:19
After: 12:46 10:1 8:1 6:1

When I tried to run on these settings, my laptop display would just turn off right before it booted into xserver and the fan would go into overdrive. Eventually, I was able to test certain settings by running the following script (I have a dual core cpu):

dp@dp-acer:~$ sudo -i
[sudo] password for dp:
root@dp-acer:~# cd /sys/devices/system/cpu/
root@dp-acer:/sys/devices/system/cpu# 
root@dp-acer:/sys/devices/system/cpu# for PHC_VID in ./cpu*/cpufreq/phc_vids; do echo "35 25 5 1" > $PHC_VID; done

...and just keep lowering the numbers until my laptop froze.

This seems to be a fairly incomplete solution though, because apparently my numbers can be lower once xserver is running, but need to be higher to start it, otherwise I get the black screen again.

Also, my laptop doesn't seem to be running that much cooler. It ran from 65C-70C before, and now seems to be 63C-68C. So not much difference. Maybe I just need to see if I can get the numbers lower. ******* runs pretty cool and quiet though, and that's aggravating!

[M4rotku]

I have the 2.6.24-18-generic kernel, is there any way to undervolt that using the same meathod? wouldn't I just need to use a different patch? I really need to undervolt due to how much I use this laptop.

Much thanks,
M4rotku

[jocko]

I have the 2.6.24-18-generic kernel, is there any way to undervolt that using the same meathod? wouldn't I just need to use a different patch? I really need to undervolt due to how much I use this laptop.

Much thanks,
M4rotku

I managed to get it working by patching the kernel source and recompiling the acpi-cpufreq module. I found this old howto, which got me started.

Here's a quick howto, updated to work on hardy (just copy-paste the commands to a terminal):

1. Open up a terminal and install subversion, the kernel source and build-essential:

sudo apt-get install subversion linux-source build-essential

2. Get the linux-PHC patch:

mkdir ~/linux-PHC
cd linux-PHC
svn co http://phcpatches.googlecode.com/svn/trunk/acpi-cpufreq phcpatches/cpufreq

3. Apply the patch to the kernel and build the module:

sudo bash
cd /usr/src
tar -xjf linux-source-2.6.24.tar.bz2
cd linux-source-2.6.24/
cp ~/linux-PHC/phcpatches/cpufreq/patches/linux-phc-kernel-vanilla-2.6.24-rc1.patch .
patch -p1 < linux-phc-kernel-vanilla-2.6.24-rc1.patch
cp /boot/config-$(uname -r) .config
make oldconfig
make prepare
make scripts
make M=./arch/x86/kernel/cpu/cpufreq

4. Replace your old module:

cp /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko.old
cp arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq
depmod

Reboot.

I hope I didn't miss anything...

[skinnie]

I managed to get it working by patching the kernel source and recompiling the acpi-cpufreq module. I found this old howto, which got me started.

Here's a quick howto, updated to work on hardy (just copy-paste the commands to a terminal):

1. Open up a terminal and install subversion, the kernel source and build-essential:

sudo apt-get install subversion linux-source build-essential

2. Get the linux-PHC patch:

mkdir ~/linux-PHC
cd linux-PHC
svn co http://phcpatches.googlecode.com/svn/trunk/acpi-cpufreq phcpatches/cpufreq

3. Apply the patch to the kernel and build the module:

sudo bash
cd /usr/src
tar -xjf linux-source-2.6.24
cd linux-source-2.6.24/
cp ~/linux-PHC/phcpatches/cpufreq/patches/linux-phc-kernel-vanilla-2.6.24-rc1.patch .
patch -p1 < linux-phc-kernel-vanilla-2.6.24-rc1.patch
cp /boot/config-$(uname -r) .config
make oldconfig
make prepare
make scripts
make M=./arch/x86/kernel/cpu/cpufreq

4. Replace your old module:

rmmod acpi-cpufreq
cp /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko.old
cp arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko /lib/modules/$(uname -r)/kernel/arch/x86/kernel/cpu/cpufreq
depmod
modprobe acpi-cpufreq

I hope I didn't miss anything...

Can I try it in 64bit version of ubuntu or it won't work?

[jocko]

Can I try it in 64bit version of ubuntu or it won't work?

I did it in 64 bit, so yes, try it. I haven't tried in 32 bit, but I guess it works with the same instructions...

Edit:tried and it worked..only thing is when doing Quote:
rmmod acpi-cpufreq
it says it is in use.
As I knew +- the values for my voltages,I did
sudo nano /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
and edited...

If the module is in use, just skip the "rmmod" and "modprobe" commands in step 4 and reboot instead.
Remember that if you have a dual core cpu, you need to change both cores.
So edit both /sys/devices/system/cpu/cpu0/cpufreq/phc_controls and /sys/devices/system/cpu/cpu1/cpufreq/phc_controls

[skinnie]

I did it in 64 bit, so yes, try it. I haven't tried in 32 bit, but I guess it works with the same instructions...

How do I setup the vids manually and make them applied every reboot?

[jocko]

How do I setup the vids manually and make them applied every reboot?

See step 5 in post #1 in this thread.

[skinnie]

See step 5 in post #1 in this thread.

Sorry I didn't notice.
I did

sudo bash
echo "11:32 10:16 8:10 6:9 136:11" > /sys/devices/system/cpu/cpu0/cpufreq/phc_controls

rebooted....
then

cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls

and obtain the default values

11:47 10:38 8:28 6:18 136:11

any clue?

I did it in 64 bit, so yes, try it. I haven't tried in 32 bit, but I guess it works with the same instructions...



If the module is in use, just skip the "rmmod" and "modprobe" commands in step 4 and reboot instead.
Remember that if you have a dual core cpu, you need to change both cores.
So edit both /sys/devices/system/cpu/cpu0/cpufreq/phc_controls and /sys/devices/system/cpu/cpu1/cpufreq/phc_controls

That's what I did...I verified that once you change the values in cpu0,it will change to the same in cpu1

[jocko]

Sorry I didn't notice.
I did


rebooted....
then

and obtain the default values


any clue?


That's what I did...I verified that once you change the values in cpu0,it will change to the same in cpu1

Read step 5 again. It tells you to add the line to your /etc/rc.local file, to have it apply during boot.
And I need to change it for both cpu0 and cpu1, otherwise core 1 will run at the default voltage while core 0 runs at lower voltage.