I recently replaced my motherboard, cpu, and memory, getting a 990fx ud3 from gigabyte and an fx-4300 cpu. In bios and in every hardware monitor I've ran, I get cpu temps as low as 4 degrees celsius, which is ridiculous. I can run prime95 and almost get it up to 30, and then it immediately drops down to around 10 degrees once it's shut off. Using the Dark Knight II Night Hawk Edition cooler from Xigmatek. I tried using a different cpu and got the same problems, so it's looking like it's definitely a mobo problem. What do I try next?
More about :cpu temps low fluctuating unrealistically mobo issue
It's not a mobo or sensor problem, it's a software problem and has been discussed here numerous times. The sensor delivers a voltage and the software relates that to a temp value. the problem now is the offset and the non linear voltage curve. From my experience the mobo makers utility and the bios has the "best guess" what the real temps are.
^ Totally Concur.
3rd party software sometimes A) does not apply the correct offset, or B) looks at an incorrect address (location). Noidea_77 probably nailed it as incorrect offset as it changes when a load is applied.
Same meat, differanent potatoes - The sensors can be one of three devices 1) a PN junction, to a current device (RTD) or a resistive device. The output normally goes to a DAC that converts it to a HEXadecimal value and is stored in a registry (Address). The software then convers the value to a decimal and applies a algorthium to provide the reading (alternatly it could use a look up table).