You cannot rely on any third party application for your temps, you have to double-check them.
Lots of Apps just detect that Nuvo chip whatever and attempt to read all the sensors what "it thinks" it's attached to the chip, not taking into consideration those sensors may not be in use at all, so you are looking at FAKE readings. Be logical, almost nothing can shoot up to 100c almost instantly, you will notice it reads that right after you boot up, maybe except the CPU itself.
For those of you who are into temps, just buy one of those IR thermometer guns, your Dad may have one, they are not that expensive, and prove to yourself whether your Mobo is really at 100c.