Windows 7 - Oc 4870

I have a 4870 1gb and the memory on the 1gb will only go to about 995 and artifacts somewhere between 995 and 1000 - however with riva tuner the gpu will clock beyond 850 from 750 - i was kind of happy with this, but found some issues after using the tv out function in ati overdrive, but i think if you steer clear of overdrive you could be successful. Firstly disable ati overdrive download riva tuner 2.24c and install - find your way to the low level overclocking and fan adjustment part and make sure you reboot when it asks you to for both oc gpu and fan control defaults - i think your memory should do between 1100 & 1200 or close to and the gpu i cant remember either, but take it up in increments of 5 to start, and when you get to artifacts go back about 15 and to be on the safe side.
The 4870 will oc nicely, but not all games repond to oclocking the graphics, as some are cpu limited, and only respond when you stretch the cpu, which is a shame, but from what i can gather, and from some of the benchmarks -crossfire will responds in some of these cases.
Go to the download section at the below site for riva tuner, and any other utilities :
nVIDIA Geforce 285 260 9800 275 295 GT GTX AMD ATI Radeon HD 5870 5850 4850 4890 X2 - Guru of 3D: PC Hardware Reviews