I have an Intel i7 4790k running on Windows 10.

But it is capped at 4.00Ghz and doesn't go higher than that.

By looking at the BIOS, the processor manages to go to a turbo frequency of 4.3x Ghz .

Is Turbo Boost on Windows 10 the culprit here? Cause the frequency used to fluctuate before this and now it remains at 4.00Ghz.