Thank you for your answer onpon4 !
Err I really wonder why companies like AMD don't release their drivers as
free software, I can't see what they gain like that..
Yeah, that's why I installed as I said in my first post the non-free drivers,
it works but it is of course non-free and they are not even done properly
(tried playing simple games and it does weird things lol).
Your solutions are interesting but unfortunately, it is the laptop which was
chosen by my school and I can't change anything on it. :S Also I can't use a
laptop cooler since this laptop (HP Elitebook 8560p) is already kinda big and
heavy and doesn't fit easily in my "bag". :C
Raaah stupid laptop they choose.
About the underclocking, I already tried that but it wouldn't work properly
(I have an i7).
