While trying to figure out why the performance of my machine has suddenly severely degraded, I noticed that although CPU temperature is being reported as 45C while idle, the temperatures of all 6 Cores is being reported as 75-80C.
I suspect these readings are correct, as my i7-3930K (3201 Mhz) is being throttled to 1600-1200 Mhz. I've also tried reconnecting everything, and continue to receive the same readings from the sensors.
What is the difference between the CPU and Core temperatures?
CPU temperatures listed by many motherboards themselves can be based on a sensor that exist under the CPU, and because that is not the actual core temps, they also have applied algorithms that attempt better to guess what the temperature might be. This could be reading about anything, a mix of the motherboard's own heat, and the CPU heat around there, and any adjustments they made to it, could be close or miles off. They could also be using the CPU package temperature.
The "core temperatures" listed by many programs is based on a sensor that intel has that sits right inside the die of the CPU itself, and reads the actual temperatures the CPU is having to deal with. Provided by Intel, along with providing the method of reading it, most motherboards still are not applying that for their own info and control.
A system sensor will often also exist, that can be based on a mix of the motherboard temps and ambient temps, or could be more about the main chipset temps for the I/O chips that exist on the board. All depending on how they wanted to do things.
CPU core temps are usually a reliable way to determine the CPU temps, for situations like throttling at ~100° C. 75-80° C an Intel modern processor should not be throttling. A modern Intel processor will happily downclock and down voltage at any temperatures, when it does not have a lot of work to do.
An operating system can also have some level of control of CPU scheduling stuff, in Windows that is in the power settings and advanced power options. The max and min performance and active and passive cooling items, can affect the processor stepping and aspects of the cooling (but not throttling specific). Also a motherboard's own thermal response system can be adjusted usually for the fans.
