100c is quite hot even for a stress test at stock speeds. You may want to double check the installation of the cooler to make sure it's mounted securely, that the base of the cooler is flat against the cpu for good contact. There's a thumb screw in the middle of the 212 evo just under the cooling fins where the mounting "X" bracket meets in the middle, try tightening it clockwise to increase mounting pressure a little. You used the included thermal paste right?