I have installed AMD Catalyst, but when I am playing something, then it is not using my GPU (in this case Garry's Mod).
My output of
glxinfo | grep OpenGL is
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: AMD Radeon HD 7970M
OpenGL core profile version string: 4.3.12798 Core Profile Context 13.35.1005
OpenGL core profile shading language version string: 4.30
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.3.12798 Compatibility Profile Context 13.35.1005
OpenGL shading language version string: 4.30
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
I can tell its not using the GPU because my CPU is as hot as hell, but my GPU is completely cold.
This is the information screen on my catalyst: http://screencloud.net/v/ebxD