[ubuntu] Driver Ati Radeon HD 4870x2

hello guys,
i decided to come back in magic world of ubuntu after many years and i decided using my PC-Desktop. I was a gamers 5-6 years ago and i o.c this PC-Desktop but after 3 years of honored career i diidn't have any nore time to play. Anyway the problem is the drivers of ATI Radeon HD 4870x2, in particular way the software to control my fun speed. I have 3 fan on my video card because i substituted the original fun with Arctic cooling. I tried reading post everywhere, installing packets or follow guides but nothing. So, please, could you help me?
My Ubuntu distribution is 14.4 LTS

Thanks