CPU idles at a low temperature but when under load it gets really hot?

[sodapopsimba]

I have an AMD FX 8120 running with a stock cooler and I added new Cooler Master ThermalFusion 400 to lower the temperature. The idle temp went down from 47-51 degrees celsius to 33-35 degrees celsius. However, when I play any video games or run a benchmark such as Prime95 for less than 10 minutes it reaches to over 70 degrees. On top of that, my Crosshair V Formula motherboard records one of its temperatures at -128 degrees celsius (though that isn't CPU related).

 

[azathoth]

Prime95 raising the temperature to 70 degrees is to be expected.

 

[sodapopsimba]

I expect that, but even random games like Team Fortress 2 will send its temperature soaring even past 80. This never happened before. It would just get to 60-65 degrees celsius and stabilize there.

The CPU is at 1.4 v and the multiplier is 17, according to AMD Overdrive.