So after overclocking it to 4,5Ghz @ 1,3V it crashed so I upped the voltage to 1,32V straight away. I ran an OCCT stress test for about 10minutes. Max temp on the cores varies from 57 to 70°. I also noticed that the clock speed went down to 4.0ghz, on idle it stays on 4.5ghz. Is that normal...