In AMD overdrive look under the CPU tab. There you will see Thermal Margin. Thermal Margin tells you how many more degree's the CPU can heat up before it starts to throttle the core speed to cool off. This temp reads backwards from the normal that your used to looking at. When it reads 30°C this means the CPU can heat up 30 more degrees before it starts to throttle. When it reaches 0°C the CPU will start to throttle the core speeds to cool itself off. I personally like to leave between 10° - 12°C before throttling to allow for ambient temperature fluctuations but as long as you are above 0° under full load the CPU is not over heating.
Is it accurate? Yes very. This is the best way to read AMD temps.
EDIT: This is the best way to...