I have a ATI Mobility Radeon HD 4650(not very powerful and quite old now) and I can play Dota 2,Left4Dead and other games on windows with no problem at all,whil

I have a ATI Mobility Radeon HD 4650(not very powerful and quite old now) and I can play Dota 2,Left4Dead and other games on windows with no problem at all,while on Linux(Ubuntu 13.10) I can barely open the games.