Arch Linux DELL Studio 1558 Notebook Video card problems

I was having problems with the fan going really fast all the time (at max speed) with my laptop, after switching from the propriety ATI graphics card driver to the open source one. The only reason I switched was because an update caused the propriety one to die, and I couldn't get it back again.

This problem is especially bad for laptops, when running on battery. The card this laptop has is:

02:00.0 VGA compatible controller: ATI Technologies Inc Manhattan [Mobility Radeon HD 5000 Series]

Anyway, long story short, with the open source driver (at least), you need to enable KMS. Its enabled via a kernel option in your boot loader (radeon.modeset=1), by adding the radeon module in /etc/rc.conf on the MODULES line. A complete explanation is here:

https://wiki.archlinux.org/index.php/ATI#Enabling_KMS

After you have done that, you can then specify the profiles, which is stated here:

http://www.overclock.net/9332962-post1.html