Getting back some battery life in Ubuntu 11.10 by disabling discrete graphics.

After getting Ubuntu 11.1o to recognise the graphics in my Intel/ATI dual-GPU laptop, only one problem remained. There is no easy way to switch between the two in Linux, and any existing solutions require a fair bit of dicking around to implement and, at the very least, a restart of the X server every time the switch is made.

While Ubuntu uses the integrated Intel graphics by default, the discrete ATI stays on, whirring its fan and gorging on the battery like a regular Augustus Gloop. Compared to 4-5 hours of battery life, Ubuntu would give me around 2 hours. Not good enough.

Since I use Windows 7 for gaming [my only need for a beefy GPU], I wondered if I could just switch off the ATI in Ubuntu altogether. After much Googling and head-scratching, I finally found what I was looking for. A massive thank-you to Matt at http://help.stedman.net.au/ for this info:

[NOTE/WARNING: As always, in the unlikely event that this effs your system, it ain’t my fault. Proceed at your own risk.]

First, to get the Intel GPU’s power-saving features, you need to edit GRUB, by typing the following into the Terminal:

gksu gedit /etc/default/grub

Find this line:

GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”

And change it to this:

GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash pcie_aspm=force i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1 acpi_backlight=vendor acpi_osi=Linux”

Save, close gedit, and run ‘update-grub’.

[EDIT: It appears that these power-saving features aren’t always reliable, which is probably why they’re not enabled by default. I’ve noticed the odd freeze when opening programs — only for 10-20 seconds or so — which don’t seem to occur when the features aren’t enabled. If you have the same problem, you may want to leave the line as “GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash pcie_aspm=force” and simply disable the ATI card as below.]

Then, to disable the discrete ATI card, type the following into the Terminal:

gksu gedit /etc/rc.local

Insert the following line to the very top of the file, then save and close gedit:

sudo echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

Then restart your computer.

For me, nothing went wrong. In fact, everything went right. Upon reboot, the ATI’s fan no longer whirred and my battery life had practically doubled. Which is freaking awesome.