Last year I built an AMD A6-6400K Home Theater PC (HTPC) with Ubuntu 14.04 LTS. The A6 has a dual port GPU processor built in.
It worked great until an Ubuntu update on Dec 12, 2014. I had been using the X-org X-server wrappers (open source, tested) until recently. But these wrappers don't work anymore.
Now I am using the latest AMD proprietary device drivers. This was a challenge.
Here is a screen shot of my current "Additional Drivers". What many don't know is that the easiest way to install the AMD fglrx
driver suite is to select option 2 or 3 below. But these do not give you the latest drivers from AMD.
I have downloaded the latest AMD drivers from here and carefully followed the instructions here. Four custom .deb files are created in a directory.
Unfortunately following the instructions failed to properly install the AMD Catalyst Control Center on my system. This was corrected by doing the following:
cd <wherever the .deb files are>
dpkg -P fglrx-amdcccle
dpkg -i fglrx-amdccle_<whatever_version_is_here>.deb
After a successful install, the Synaptic Package Manager should display something like the following after filtering out `fglrx':
Note the 2:14.501 version tag. The current updated Ubuntu LTS default is 2:13.350.
The CCC lets you configure and tweak your AMD graphics, The instructions above discuss dual GPU configurations. Read them carefully. And maybe there is some way in the BIOS to disable the Haswell Mobile or select the AMD GPU.
Good luck. I use the Ubuntu 32 bit OS and the Radeon 8470D driver on the A6-6400K. One of the defaults was an 8% underscan. This made my 50 inch TV display a 46 inch picture. I have no idea why this would be a default. But everything works great again.
Your mileage may vary.