AMDGPU/Radeon Graphics under Ubuntu 16.04

Ubuntu 14.04 had the proprietary AMD driver fglrx-core which was deprecated in 16.04 release. So if anyone upgrading from 14.04 to 16.04  needs to be aware about this. After the upgrade that driver might not be available. If it did left befind after the upgrade it would cause problems and it would crash from time to time due to incomparability. 

Users of Ubuntu 16.04 can use the open source version of the AMD driver.

So if you've previously installed the ATI binary/proprietary driver (a.k.a Catalyst/fglrx), you need to make sure it's fully purged before trying to use the open-source ati/radeon driver.

That can be archived by the flowing commands.

sudo apt-get remove --purge xorg-driver-fglrx fglrx*
sudo apt-get install --reinstall libgl1-mesa-glx \
                                 libgl1-mesa-dri \
                                 xserver-xorg-core

sudo dpkg-reconfigure xserver-xorg

source

For the most recent ATI/AMD graphic cards supported by the Radeon driver, DPM (Dynamic Power Management) should work automatically without additional steps. 

Instead if you notice overheating problems and/or you have an old Radeon HD graphic card, you can enable DPM by adding a boot parameter. This should greatly help power consumption, especially when idle. To do so, edit /etc/default/grub and add the 'radeon.dpm=1' to the GRUB_CMDLINE_LINUX_DEFAULT line, 

so it would look something like:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.dpm=1"

After you save/quit the text editor, update grub:

sudo update-grub