I have tried several solutions but nothing works. First of all, I'm using ATI Radeon HD 5400. The first monitor (which works) is connected to the graphic card by DVI, the second monitor (which isn't detected) is connected to the motherboard by VGA. One important point - when I used Windows (yesterday?) the two monitor worked together fine.
What I've done until that moment:
Followed by the instructions here: https://help.ubuntu.com/community/BinaryDriverHowto/ATI#Installation_via_the_Ubuntu_repositories. Installed
sudo apt-get install fglrx. Then typed
fglrxinfoin the Terminal and got:
display: :0 screen: 0 OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: ATI Radeon HD 5700 Series OpenGL version string: 4.2.11903 Compatibility Profile Context
System Settings > Details > Graphicsdisplays
The second monitor isn't detected either by the
Catalysit Control Centernor by
System Setting > Display.
$ lspci | grep VGAdisplays >>
01:05.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI RS880 [Radeon HD 4200] 02:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Juniper [Radeon HD 5700 Series]The meaning is that it knows about the existence of the on-board graphic - Radeon HD 4200 (?).