The CPU will automatically throttle (slow down) at around 90C, so that it is not damaged. Ideally, you should be able to run a CPU torture test, and keep the temperatures in a reasonable range, say 60C to 75C. I suggest you look at the setup you have for cooling. Do you have enough large fans pushing air through your case ? Are the fans orientated correctly ? i.e. the air should flow across the CPU, with a more-or-less balanced number of intake and exhaust fans. Perhaps your fans are set to run too slowly? Also check that your CPU cooler is the correct capacity for your CPU, and that it is properly attached with not too much thermal paste.