OfficialJJTech :
91 degrees is very high. Get a better cooler. Try to keep your cpu temps under 80 degrees. if you reach 110 degrees you can fry your cpu. Overall, just get a better cooler.
The system will shut down before the CPU gets hot enough to fry.
Niokiryth :
I recently got a NH-D15. Before this I used a Hyper 212 Evo. It thermal throttled at full load ≈91°C as reported by XTU and at 100% utilization. The CPU is overclocked to 4GHz. Is the new temperature good?
Did you remove the protective plastic on the heatsink before installing it?
Did you notice if there was thermal compound on the heatsink?
Did you clean the old thermal compound off of the CPU before installing the heatsink?
captaincharisma :
you need a better cooler if you plan to overclock.
What do you know of that's better than the NH-D15? The cooler is a beast.