Gigabyte z170x Designare OC problem

Does anyone know how to set turbo boost above 4GHz for Gigabyte z170x designare?

CPU doesn't boost (I've got i7 6700K) on auto and stays on 4GHz and even when I run CPU stress test stays on 4G,
I've notice that in BIOS both multiplier values are 40 but when I change value to 46 it change it only in 1st column (idle) not boost - this one stays 40 (4GHz) and CPU stays on 4.6Ghz even when idle.
I'm using an integrated CPU graphics for now but I think it shouldn't affect it.
CPU temp on 4.0G = 30C and 4.6G = 35C (I've got water cooler)
I've updated the BIOS to F20 version as the same problem I had with previous - preinstalled one. What can I do with it - I don't wont to run CPU on "boost" speed constantly.
Could someone please help me with it?
I bought this motherboard from overclockers.co.uk so I think this is the best place to ask for help.

Haven't had the pleasure of playing with that motherboard but here's a few simple checks:

Intel Speed Stepping enabled?

C-States enabled/Auto?

Windows Power option set to Balanced not High Performance?

I have the same motherboard from Amazon. Your temps seem perfectly fine running at 4.6Hz. By default if you overclock the bios sets all cores to run at max frequency when needed. As long as you select balanced power profile and set your cstates to auto/enabled the OS will down-clock/down-volt in order to save power. F20 also features Speed Shift which I would enable to have the maximum responsiveness of frequency scaling.