8700k can't get past 5.1 Ghz. Lacking CPU power or bad chip?

[thtran6]

Hello guys,

So I have an i7 8700k overclocked to 5.1 Ghz all cores at 1.34 Vcore.
The above setting was stress tested with Prime95 version 26.6 (non-AVX) small FFT test for 8 hours without crashing.
Temperature stays under 65C because this chip was delidded and plus I'm using the EVGA 280mm CLC.

So that was pretty stable to me.

However, when I want to try 5.2 Ghz, no matter how much Vcore I increase, prime95 still crashed and BSOD within 5~10 minutes. I have tried going from 1.346 Vcore all the way to 1.40 Vcore. Temp was never a problem so it must not be thermal throttling.

To me, the extra 100 mhz isn't a huge deal. I just want to understand what's going on here.
Do you think this is due to the "bad" chip that has a limit at 5.1 Ghz?
OR, do you think this is due to the lack of CPU power?
(due to the fact that my Z370 motherboard only has 8-pin CPU_PWR connector, as opposed to Z390 mobo which typically have 8pin + additional 4 pin CPU_PWR connector)?

In other words, do you think the 8-pin CPU_pwr connector can provide enough power to the i7 8700k at 5.2~5.3 Ghz all cores?

My spec:
i7 8700k
32 Gb ram
RTX 2080
EVGA G2 850W
MSI Z370 A-pro motherboard

 

[bniknafs9]

why do you expect to go much beyong 5 ghz . most articles say i9 9900k is the road to 5 ghz . from what it seems you have to wait for their 10th and 11th series if you wanna go much beyond 5 ghz .

 

[thtran6]

why do you expect to go much beyong 5 ghz . most articles say i9 9900k is the road to 5 ghz . from what it seems you have to wait for their 10th and 11th series if you wanna go much beyond 5 ghz .

I have an i7 8700k bro :\

 

[bniknafs9]

maybe the chip matters too , like if you had an asus motherboard in the first place one of those extreme rampage stuff

 

[Rataan]

I never heard of anyone who thought 5.2 GHz from an 8700K was a sure thing. You're using an AIO and what is frankly an entry level Z370 board, so it looks to me like you have done pretty well considering the hardware.

 

[1LiquidPC]

You have a good chip to even get 5.1 all-core at 1.34v. Only the top binned CPUs will get to 5.2 or 5.3 stable at any voltage. All CPUs hit a wall of sorts when OCing after certain point. To get the extra 1X multiplier of speed requires massive voltage and temp increase. Where the wall is is specific to each CPU. LLC also comes into play to account for vdroop. Recently sold my delidded 8700k, and it required 1.385v for 5.0Ghz all-core.

 

[kgt1182]

8700Ks hitting 5.2-5.4 GHz are extremely binned chips under custom loop cooling, where lower temperatures allow higher clocks at the same voltage or higher safe voltages by virtue of reducing silicon trace resistance.

Getting 5.1 GHz on an AIO on 6 cores is considered very lucky. Overclocking is not a sure thing. Some people may not even hit 5.0 GHz. Be satisfied with your +1.5 GHz Overclock.

You will see greater gains increasing the RAM, Uncore (Ring) and GPU from here onwards.

Have a good day.

 

[thtran6]

Thank you for all of your answers guys.
It was kinda annoying since the chip was able to do 5.1 GHZ at 1.34 vcore and 65C under max load but still can never get that extra 100 mhz at the expense of 1.40 vcore.

I guess the chip has hit that "wall" that everyone has mentioned.

It's still good to know that the cause was due to the chip itself and not the lack of CPU power. That was my main concern since it would really suck to have a really good chip meant to run at 5.2 ghz or more.... only to be held back by the lack of cpu power from the motherboard.

On a side note, my new motherboard - MSI Z390 MPG Gaming Pro Carbon AC (with 8pin and additional 4pin cpu pwr connector)- will arrive this Friday and I will update everyone if anything magical happens.

If not, I'm still happy since new mobo = better vrm heatsink anyway.