Whenever I try to play a game it crashes after 10-20 minutes to a sound loop with the screen receiving no signal, forcing me to do a hard reset. My videocard is a Radeon HD7970. My system worked just fine for a year and a half but started to crash every single time since two days ago. I have monitored the temperature of my GPU during the latest crash (running farcry 4) and at 87 degrees celsius it crashes. Other games like Evolve make it crash too. What should I do?