Battery life on a T420

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Baby Hen
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Joined: Wed Nov 02, 2011 3:07

Battery life on a T420

Post by 30thElement » Wed Nov 16, 2011 5:28

I have a T420 with the 9-cell battery, because Lenovo claimed, and reviews confirmed, it get's over 10 hours on battery life. However, I'm only getting somewhere between 4 and 5 with Sabayon 7-xfce. I've seen a few places saying that adding "pcie_aspm=force" to the boot commands will fix it, but either I'm not adding that line in the right place or it isn't helping. I'm also on the new i7, if that changes anything.

Simple Hen
Posts: 68
Joined: Wed Sep 07, 2011 0:46

Re: Battery life on a T420

Post by King_DuckZ » Tue Dec 20, 2011 11:40

In my experience Linux is quite an energy hog. The best combination I could find is to use Debian with vey low screen brightness. For some reason Debian seems more efficient than other distros I tried, but it's just my impression, nothing I measured. I also installed powertop. When I run on battery and I want to squeeze the most out of it I just disable everything from powertop, then put all files I will work with on my SD card and the rest in a ramdisk. That way the HD will stop spinning too. I also turn off the wi-fi switch.
All of those things also apply to Sabayon, so you might have a try. Anyways, it all depends on what you're going to use.

I recall a colleague telling me about this new technology on mac books that allowed the OS to automatically switch from the main graphic card to the integrated chip when the gpu wasn't needed. Apparently this saves a lot of power, but I don't think anything other than apple computers can do that.

Simple Hen
Posts: 58
Joined: Tue Jun 17, 2008 19:51

Re: Battery life on a T420

Post by Ramiliez » Fri Dec 30, 2011 19:02

GPU switching can be done on Windows Laptop too and NVIDIA calls it Optimus but it doesnt work in Linux because NVIDIA will not support it on Linux and probably never will

According to this article AMD GPU switching works under Linux ... &px=OTI3Mg
Sabayon 9 x64 KDE

Sagely Hen
Posts: 2718
Joined: Wed Nov 26, 2008 16:41

Re: Battery life on a T420

Post by micia » Fri Dec 30, 2011 23:46

In my experience kernel linux 3.1 helped a lot my laptop to behave correctly in energy saving, you can use kernel-switcher to get it easily.
I also suggest you to install and activate irqbalance and microcode-ctl, as well as cpufrequtils (if it isn't already), as follows:
(as root)

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equo install --ask microcode-ctl irqbalance cpufrequtils
rc-update add microcode_ctl default
rc-update add irqbalance default
rc-update add cpufrequtils default
Reboot to make these changes effective (or start each daemon manually).

I also suggest not to unload the microcode module, since it is safer to have it always loaded for the microcode update to survive events like suspension and individual core shutdown.
Edit /etc/conf.d/microcode_ctl file, as root, with your favourite editor, changing the line:

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