gpu frezzes

As I mentioned, the screen freezes when I start playing and the core clock is on factory settings, but the problem is solved when I lower the core clock to -200 MHz . I don't know why I have to lower the core clock from its base speed. I have been playing on the same factory settings in the past...

I am putting together a new rig and I would like some HELP on whether the evo 212 will do cooling the i5 6600k. Also whether this rig seems okay. The power supply bigger because I will get another Gigabyte gtx 970 g1 next year. 1. I5 6600k may overclock it in the future. 2. Gigabyte gtx 970 g1...