i7 8700k won't overclock past 4.5GHz

[Graptik]

Hi, I recently bought an i7 8700k and am trying to overclock it to at least 4.7GHz. Unfortunately I can not get it stable at anything past 4.5GHz even at 1.4v. This is using fixed voltage. I am using OCCT to test stability and so far I have only got to 4.5GHz using 1.3v. Another thing I've noticed is that even when using the highest LLC level available, the voltage under load still drops around 0.3v below what I set in the BIOS. Temps are very good even when using 1.4v. Any help at all would be greatly appreciated.
Specs:
CPU:i7 8700k
Motherboard: ASRock Z370 Pro 4
GPU: Nvidia GTX 1080ti Founders Edition
RAM: 2 x 8GB Corsair Vengeance LPX 3000MHz
Cooler: Corsair H75 AIO
Storage: 2 x 1TB
Power Supply: EVGA 600w 80 Plus White

 

[Graptik]

If you look at his guide on overclocking the 8700k, the ASRock Pro4 is shown in comparison to other boards and it shown in the guide as being able to hit 5GHz.

 

[Graptik]

sorry, should be more specific, the statement at 10:35 and beyond.
also you're using an aio cooler = no air to the VRMs, i'd be wary running those kinds of voltages as the VRMs likely wouldn't cope and thermal throttle.
1.3v should see the cpu at 4.7-4.8ghz on all cores, unless you've lost the #siliconlottery

Oh okay now I understand. I am using an AIO but I do have a case fan pointing directly down onto the VRMs. Also, as I mentioned in my original post the voltage always seems to be 0.2 - 0.3v under what is set in the BIOS, so 1.3v in the BIOS will in reality be about 1.27v which I wouldn't think would be enough to throttle the VRMs? Also I have been using the correct LLC - Level 1 (opposite to most boards I know).

 

[Graptik]

That's 0.02-0.03V or 20-30mV.

Are you using HWMonitor to track the voltages?

Yes sorry I meant 0.02-0.03v. Yes I am using both HWMonitor and CPU-Z to check voltages. Obviously not both at the same time but they both show the same result.

 

[Graptik]

Occt ?? Use real bench or some real world test. Do you play occt??

I don't use this junk but I am sure later versions are avx enabled which again is torturing the cpu.

An easy way to get more if your just gaming is disable HT. Often infact improves games.

It also crashes in regular gaming use at anything more than 4.5GHz so it is not stable at all. 4.5GHz is rock solid at 1.3v (more like 1.27 after the voltage drop).