Radeon HD 4870 GPU clock stuck

Hi,
As I am intelligent ( :whistling ) I purchased a Radeon HD 4870
But , after installing the drivers, any game, anywhere, crash in 2 minutes while the card is 45 °.
Apparently, the GPU clock is stuck at 200mhz ram and suffered the same fate
As I am not a fanatic of ATI, the Catalyst is unknown to me, you have a solution?
Thank you all

you plugged the jack PCI-E on your card? drivers? 8.12?

Yes 2 connectors connected, and the 8.12 drivers installed 3 times, and it starts walking

not hesitate to format when u feel that there is a bug-level software, because often the driver uninstaller only half the work and ultimately it shows that time wasted