It is totally normal to see a difference of 20 degrees Celsius between cores on Intel processors, even if the system is in idle.
This is because there will always be a core that will have more load than the others, so it will always have a higher temperature.
In fact, you do not need to worry about the cores temperature; you need to pay attention only to the CPU temperature itself, but not to the cores.
Please read the following thermal information:
The TCase for your Intel Core i5-3570K is 67.4 degrees Celsius.
The TCase is a number established by Intel® as a point of reference in order to understand what could be expected as per normal processor temperature.
Anything from the Tcase and below will be the expected temperature of the processor in normal use, anything that doesn’t stress out the processor (watching movies, burning CDs, browsing the internet, creating documents, etc.) When the processor is stressed out meaning that you are running heavy processor applications that take control of the CPU or uses it at 100% the temperature will go beyond the TCase. It can perfectly reach 80 to 85 degrees and the processor will still be OK. The cooling fan is in charge to keep that temperature there.
If the processor temperature reaches 100 degrees or higher it will send a signal to the motherboard to shut down to prevent mayor damages and most likely it won’t be possible to turn the computer back in until it cools down.
The normal processor temperature will depend on the chassis type, the hardware involved and the location of the computer, and it usually is lower than the TCase.
Remember that this is CPU thermal information, not cores temperature.
Thank you sir,
I also still have a couple of questions; I still see the core at the same temp even when it is @ 0% load? I also saw some users who have the same processor with the same fan, but it seems like they do not have such a difference among cores. However, in my case, when the CPU is under 100% load, the difference in temps decreases to 5-7 C between those two cores. Here are two pictures when it is idle and under full load.