Intel Core i7-4770K - healthy core speed

Intel Core i7-4770K core speed

Is my i7-4770K ruing at higher core speed than it should? The core speed is usually around 3.9 GHz according to CPU-Z. I expected it to stay close to the processor's base frequency (3.9 GHz) and not always at max turbo frequency (3.9 GHz).
I haven't overclocked. Windows 10 power plan is set to high performance.