If you have new AMD/ATI graphics notebook or desktop then i am quite sure you are facing Driver problem. I did also. From my experience i will describe the best driver for ATI and also why.
There are two kinds of driver exists.
1. Provided by ATI company
2. Open source Driver (Developed by ubuntu developer)
Best Driver ever: Open source driver (Gallium3D / Gallium 0.4
Why should not use ATI provided driver ?
Because it is a handicap driver. ATI developer just simulate windows 3D driver working procedure. So it does not provide best service for Xorg.
Open source driver is the best with KMS support. Now question is how could you install it? Way is too simple. It is already installed and you need to just enable it.
Step1: Remove AMD provided (catalyst) driver if you have install it link.
Step2: Need to help kernel to detect your hardware specification. KMS(Kernel Mode Settings) is best way to do this. It automatically detect hardware in boot. Do not need to manually change /etc/X11/xorg.conf
Step3: Enable KMS ->
sudo gedit /etc/default/grub
Find this line GRUB_CMDLINE_LINUX_DEFAULT = and replace the line with GRUB_CMDLINE_LINUX_DEFAULT=radeon.modeset=1
Save and close the file
Step4: Update the grub: sudo update-grub
Step5: Restart and after restart kernel will automatically detect your PC's hardware.
Step6: You can see your driver information from System settings-> Systeminfo
Step7: See the Frame rate : glxgears [output should be around you monitor refresh rate(60)]
Step8: Your Graphics card information : glxinfo | less
Step9: Test your graphics using these options: glxgears or glxheads or glxdemo