Been using this program for years and today I found out something about it that I didn't know it could do.
CPUz can tell you the speed of all the CPU cores at the same time, just
right click on the core speed out-put box. Up to today I have been using a program called Speccy to do it

In the attachment you can see that 3 of the cores are under clocked while core 1 is at maximum. The speed dose constantly change on all cores, that is what it was displaying when I did the screenshot.