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I don't have an AMD graphics card so I couldn't test this, but failsdownloads reader towpik, who sent us this tip, says that using this feature, "the laptop is very cool and quiet. Finally!". Also, according to Phoronix, Radeon DPM is "fantastic for power use [and] thermal performance".

Please note that this will only work for Radeon HD 2000 graphics cards and newer.

1. To enable DPM in Ubuntu 13.10, you need to open /etc/default/grub with a text editor (as root) - I'll use Gedit below:

gksu gedit /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

radeon.dpm=1

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.dpm=1"

sudo update-grub

For Ubuntu 13.04 and older, you need a newer Kernel (since Linux Kernel 3.11 or newer is required) as well as an updated firmware. Since there are many things that can go wrong and I am not able to test this because I don't have an AMD graphics card, I won't post installation instructions for these here, but if you really want this, try these instructions.

Currently, the PPA ships Nvidia drivers only (and it's not clear if it will include other packages like AMD drivers, etc.) and is in testing. According to the PPA description, you should wait a few days before using this PPA.

In a message posted on the Ubuntu Desktop mailing list, Jorge O. Castro notes that currently there's no difference between this and the xorg-edgers PPA and that "the real fun begins when new drivers are released".

At the time I'm writing this article, the PPA provides the latest stable Nvidia driver (352.30) as well as the latest beta (355.06), along with libvdpau 1.1 and vdpauinfo 1.0, for Ubuntu 14.04, 15.04 and 15.10, with some older packages (Nvidia 346.87) for Ubuntu 12.04.

To add the PPA (but again, you shouldn't be using it until the PPA description says it's safe to do so), use the following commands:

sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update

and then use Synaptic / Ubuntu Software Center to install the Nvidia driver version you want to use.

1. nvidia-prime 0.5 has been released today with a new feature that allows users to switch between the integrated and discrete GPU ("prime-select" command line tool). Other changes include:

Currently, nvidia-prime 0.5 is available in the Ubuntu 14.04 Trusty Tahr proposed repository and it will take a while before it's promoted to the main repositories.

2. Thanks to the latest nvidia-prime, we can also see a change in Nvidia Settings that landed about two weeks ago in Ubuntu 14.04 Trusty Tahr: an additional tab was added, allowing users to switch between GPUs:

This tab is only visible if nvidia-prime >= 0.5 is installed. After changing between the Nvidia and Intel GPUs, you'll need to log out or restart the system to apply the changes.

3. And finally, xorg-server was updated (version 1.14.4.901) with various Nvidia Optimus fixes, including a patch to fix GPU screen output hotplugging. Like the latest nvidia-prime, this update is only available in the Ubuntu Trusty proposed repository for now.

In my test under Ubuntu 14.04 LTS with these updates installed, I noticed some important improvements: there's no more screen / GTK theme corruption, my external monitor works out of the box (connected via a mini DisplayPort port that's hard-wired to the Intel graphics adapter; connecting a monitor via HDMI which is hard-wired to the Nvidia card doesn't work) and the temperature seems lower than in my previous experience with this under Ubuntu 13.10, although it's still a bit too hot for everyday use, at least with my laptop.

More Nvidia Optimus fixes will probably follow since Ubuntu 14.04 Trusty Tahr is in its early development stages and there are about four months until it's released.

If you want to try this out in Ubuntu 14.04, firstly enable the proposed repository (not recommended!) and then simply follow the instructions from HERE.