Drops processor frequency

Somehow decided to change my old 750ti in 1660s and now doing the tests I noticed that the CPU hangs in games at a frequency of 3.57, tried to understand her and noticed a pattern when I go to menu in game, load the graphics card crashes and gives 3.8 percent honest, as soon as I go out from the menu card is loaded up to 40%+ the percent rises to 3.57, how to deal with it?
setup
i5-4670
1660s
ga-z97x
cx600