Undervolting CPU?

I was wondering about Undervolting my CPU under Linux. I had my P-M 740 1.73GHz undervolted significantly using NHC under XP, and got nearly 5 hours battery life out of my z63a with 50% brightness and wi-fi off, which is a nice amount of time when you have a couple two-hour classes in a day.

granted the battery's nearly a year old now, but the best I can muster is about 4 hours, 15-20 minutes with presumably the stock voltages. is there any way to undervolt the CPU in Linux?

 

that was kinda nubcake of me, didn't bust out my google-foo first.

http://ubuntuforums.org/showthread.php?t=146366 <info specific to Ubuntu and derivatives

http://www.thinkwiki.org/wiki/Pentium_M_undervolting_and_underclocking <this pertains to thinkpads, but should work with any lappy/distro. includes info on being able to dynamically set the voltages

 

Thanks for posting the links. It's always nice seeing people's solutions, they too often say "nevermind, I solved it!" and no one else learns how.

 

yeah... I hate that too.

I'll be honest I haven't done it yet, since every time I've tried to complie a kernel in the past I've hosed my install, despite following all the directions and guides I could find. Although, it sounds like with Ubuntu you can just select the ubuntu defaults with the patch applied, but I'm gonna leave it alone for now. Would be a pain in the butt if they backported 2.6.18, gotta compile again.

 

If you compile a kernel the Debian way (i.e. using kernel-package) hosing your system should be very unlikely. AFAICT the guide in the link below looks okay, although you might prefer to use the Ubuntu kernel source rather than www.kernel.org. (My personal preference is the latter).

http://www.howtoforge.com/kernel_compilation_ubuntu

At the end of the process you install a custom kernel along side your current Ubuntu stock kernel. If you've made a mistake in configuring your new kernel (e.g. de-selecting a crucial driver) it is very easy to reboot and select the Ubuntu kernel (from memory I think the Ubuntu distro has Grub configured to effectively hide the grub menu but hitting <Esc> at the start of the boot ought to show the Grub menu).

 

timber, I pretty much figured all of what you mentioned, but I'm also a little busy with school and such, but those pages are definitely in my bookmarks, perhaps over christmas break.

 

gentoo wiki has P-M undervolt solution