1.Your win7 must have SP1 and all available updates. If your win7 doesn't update automatically - try this solution
3.Set power limit to +50 (Radeon settings>Gaming>Global>Global WattMan)
4.Try 16.11.5 driver
5.Try another PCIe slot
6.Show me GPU-Z main screen
7.Run HWinfo64>sensors only>Logging start and play for 15-20 min. I want to see that log
Did you ever fix the problem. I am having same problem.