If I overclock the core anywhere above 850 MHZ, the screen goes black, then reappears with a message saying the driver failed. This happens again as soon as I open another app. My PSU is 480W. Could it be the problem?
More aboutproblem overclocking radeon 6670
You can't really overclock that much for HD 6670.
AMD Overdrive allows up to 960 mhz for the core clock ,but I can only go to 850 without the driver failing.