I have a radeon hd 6950 and it's running kinda hot (not much, 60c), but on Windows I noticed the fans run faster and the temp is lower.
I know I could use aticonfig, and I tried it. I installed the proprietary FGLRX driver, at first it looked fine, the GPU temp was lower without any configuration, but then I tried connecting my second monitor, and when I rebooted first it hanged at the login screen saying "logging in...", then it logged in, but the graphics were all weird (like with a very broken vga with weird lines and color everywhere, nothing on screen was recognizable) and keyboard and mouse had no effect.
So I uninstalled everything and I am back with the default drivers (which kinda flicker at login but I can live with that as long as the system is stable).
Is there any other way I could increase the speed of my GPU fan? maybe installing aticonfig but not the driver? is it possible?