I7 6700k not overclocking

[hardwareasus]

Hi,

My i7 6700k runs fine. Overclocked today, 4.5ghz at 1.3V stable.

Multipler is 40× and bclk ratio is 110.

I can't increase it anymore. For example, I put 115. It reduces the cpu frequency to 4485 mhz?

Switching turbo mode on and off doesn't make a difference.

Mobo: Asus maximus ranger viii hero

Help please.

Thanks

 

[hardwareasus]

I had to change the "CPU core ratio" from sync all cores to auto or per core.

Why is this?