How do I know if my cpu is overclocked?

[NeymarX]

the reason I ask is because in the bios at the top it states my i54690k is 4x 3.5Ghz . same on the "system" icon within windows. but when I use the msi gaming app its 1 click overclock button restarts the pc and it tells me its @ 4.0Ghz...which is it? thanks

 

[WalvisM]

The i5 has build in turbo technology so when you need more performance it will raise the clocks speed yo 3.9 or 4ghz