Why does the processor run at a frequency lower than the nominal?

Question

Processors

Everything is very strange, but I will try to explain. I decided to play Arma 3, 8 GB of RAM 1333 RX 580 4GB I5 760 (overclocked to 3.5) and saw 20-25 frames there, although there should be at least 40. I turn off the game and see in the task manager 2.2 Hz. OK, I turn off the computer, I rearrange the voltage to the percent, iiii, nothing has changed, here I already began to understand nothing. I reset the bios to the standard, the percentage started working at all at 1.2-1.5 Hz. OK again did overclocking only to 3.8 lowered the timings of the RAM 9 9 9 24 set the voltage to 1.250, I go in the dispatcher still 2.2, Aida and the CPU shows 3.4 Hz. I think, okay, I go into the arma, I still see 20-25 frames and the statistics where it shows the frequency of the processor is 1.935, I tried to move all 60 frames, but then I noticed the strangest thing,

Answer 1

So, did you turn it off to automatically prescribe voltages and frequencies? What is the motherboard.

Answer 2

Disable Windows Fast Startup in Power Options.