Ok I've always used ati catalyst drivers however given that this is broken in kernel 4.2 and I see people always saying to just use the open source ones I did just that in my Ubuntu 15.10 install.
When I have the proprietary drivers installed and use kernel 4.1 to boot everything works. Screen 1 1920x1080 and screen 2 1440x900 and displays in extended mode as intended.
However when I now use the open source I have a mess.
Only one monitor display actually seems to be detected as in Displays under settings only one shows up. It's set a screen resolution of 1280x1024. Both displays are displaying content but it is exactly the same content. I wouldn't call it mirroring as such given that it doesn't recognise both displays. xrandr shows this:
xrandr: Failed to get size of gamma for output default Screen 0: minimum 640 x 400, current 1280 x 1024, maximum 1280 x 1024 default connected primary 1280x1024+0+0 0mm x 0mm 1280x1024 0.00* 1152x864 0.00 1024x768 0.00 800x600 0.00 640x480 0.00 720x400 0.00
Under the proprietary drivers I had my 1920x1080 showing as Screen 0 and my 1440x900 showing as CRT1 in xrandr with all the different resolutions.
Can anyone help me sort this mess out?
Edit for more info:
My graphics card is Radeon HD 6850 and it's connected to a 32 inch Samsung TV through HDMI and and 19" VGA monitor connected via a VGA to DVI converter to DVI on the graphics card.