Help With Kaby Lake OC

[moobox]

Hey there I've just started experiencing a problem with my OC and was hoping someone could help.

7600K (4.8GHz @ 1.3V, core ratio @ 4.5GHz)
ASUS ROG STRIX Z270H

I had my overclock dialed in and stable, great temps. Then loaded XMP profile for my RAM as to set the correct timings. Saved in the BIOS and rebooted, then I see that my CPU is set to 3.8GHz not 4.8GHz. Also in Task Manager my CPU speed jumps around from 1.0 to 2.0 GHz.

Went back into BIOS and confirmed baseclock, multiplier, voltage and that it's showing target frequency at 4.8GHz. Back in Windows, same thing.

http://imgur.com/a/oXcSo

 

[PhysX_HW]

What happens if you turn off XMP and set the speed manually?
Have you tried resetting the BIOS?

 

[L0stChild]

make sure u save settings before you F10 to save & restart. always re-check vcore value anytime you hit that page before restart.
set load line calibration high. this will give cpu constant voltage
I usually set my uncore .1ghz lower than core, maybe set your uncore to 4.7ghz

windows settings
power options,
advance settings,

sleep off,
pci-e link state off,
processor power management:
min state 100%