8700k won't overclock past 4.5GHz

Graptik · 28 Jul 2018 at 23:10

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 · 29 Jul 2018 at 12:44

acemastr said:
Use LLC6

Does it run 4.7ghz turbo speeds when everything in the BIOS is stock?

On my motherboard LLC is the other way around and LLC level 1 is the highest. And yes it does boost to 4.7GHz.

Graptik · 29 Jul 2018 at 15:51

acemastr said:
That's good news then. Is the BIOS updated to latest?

You say the voltage drops 0.3v? That would take it down to 1.1v, did you mean 0.03v?

The BIOS is updated to the latest version. It will boost to 4.7GHz on one core but if I activate multicore enhancement, it will drop to 4.3GHz. Also, I did mean 0.03v not 0.3v sorry.

Graptik · 29 Jul 2018 at 15:57

acemastr said:
What are your temps? Something odd is going on

Temps are great, around 65c-70c in Prime 95 and OCCT with 4.5GHz 1.3v. Even when I tried 1.4v the temps only reached around 82c maximum.

Graptik · 29 Jul 2018 at 16:00

acemastr said:
Are you using the latest OCCT and Prime? Both of them are AVX which really hammers to CPU. What AVX offset are you using?

Try prime 26.6

I have been using the latest OCCT but have been using Prime 95 26.6 already. I have primarily been using OCCT to check for stability so I'm wondering if this perhaps has something to do with it as I haven't set an AVX offset.

Graptik · 29 Jul 2018 at 16:23

acemastr said:
I have no choice but to use offset 3 on my 5ghz, it fails immediately otherwise.

In Der8auer's 5GHz guide he recommends running a custom Prime 95 test with a maximum FFT size of 1344 and "run FFTs in place" checked for one hour as a stability test. Do you think this will more or as reliable as a stability test as OCCT?

Graptik · 29 Jul 2018 at 16:32

acemastr said:
Prime is actually the most intensive test I believe, it'll stress the cpu more than most tests

Okay I will test with Prime now then. I knew the new Prime95 versions use AVX but wasn't at all aware that OCCT did so thanks for that. I will let you know how Prime goes.

Graptik · 29 Jul 2018 at 17:20

acemastr said:
Prime is actually the most intensive test I believe, it'll stress the cpu more than most tests

Just tried Prime95. Unfortunately anything over 4.5GHz is still unstable. It's fine running prime for about 25 minutes and then it locks up and I have to restart the PC. So I still cannot get above 4.5GHz no matter what voltage and even without using AVX.

Graptik · 29 Jul 2018 at 18:37

acemastr said:
Leave LLC on auto and try it.

I guess there's a chance you received the worst CPU and that's the reason Intel don't put all cores on 4.7ghz turbo. That would be very unlucky though

Just tried it. Using Auto LLC made the voltage drop straight from 1.35v to 1.21v as soon as Prime started. Level 1 seems to be the only halfway decent LLC setting it still drops 0.03v below what is set in the BIOS. Really losing my patience here as most people say 4.7GHz shouldn't require anything but the multiplier to be changed.