Delidded 8700K @5Ghz @ 72-78degC Max under Prime95 @1.424V - good idea?

SledDriver

SledDriver

SledDriver

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Just got a new delidded i7-8700K from 8-Pack and it's very impressive. Running stable at 5GHz idle and 4.7GHz under Prime95, showing 1.424V idle and 1.280V vCore running Prime95 Max heat test and core temps sit between 72 and 78 degC after 1 hour. Seems totally stable. Mobo is Asus Prime Z370-A with DDR4-2666 XPM memory.

Just using the 1-click ASUS Fast/Extreme overclock function on the Easy BIOS page at this time - zero manual tweaks, as I am a beginner.

Well I say 5GHz and 1.424V, but as soon as I fire up Prime Max heat test the clock drops to 4.7GHz and the vCore drops to 1.280V. Not quite sure I understand what is happening here. Why doesn't it stay at 5GHz? It stays at 5GHz on all cores running CineBench on the exact same configuration, with vCore of 1.328V while that runs.

Idles at around 27-29degC. Recovery from higher temps takes only a second or two.

I also have all power saving tech disabled on purpose (SpeedStep, C-States, Turbo, SpeedShift) as advised for timing critical music recording which is the prime use of this machine.

But I worry about the vCore voltage - (I'm new to manual overclocking, although I have run and continue to run a very old machine with a Q9650 on an Asus mobo which was OC'd from 3GHz to 3.6GHz and ran for years completely stable.)

At 9mins 53sec into this video:

https://www.youtube.com/watch?v=SSKLAaCyD2Y

8-pack specifically says that up to 1.425V is fine on this CPU.

I have very good air cooling which seems to be coping with the delidded CPU just fine.

But what does 8-pack mean when he says 'fine' at 1.425V. Is that voltage acceptable so long as the temps are well controlled? Or will it still stress the chip and shorten the life/reliability of the chip longer-term, even with the lower temps? My vCore Max is showing as 1.440V in HWinfo64.

So my vCore is 1.424V when not under load, but drops to 1.280-1.328V under load. Is this OK, or would I be better off running the chip a bit slower, or trying a lower vCore voltage? If so, is that simply a matter of selecting a lower voltage for vCore in the BIOS, or should I be changing other settings too? I had a look in the UEFI BIOS and it's not so obvious what I change. Really don't want to blow anything up! :)

What matters to me is robust longterm reliability, but with as much performance as I can get while not sacrificing that requirement.

Any help for a newbie to this would be well received.

Cheers,
SledDriver
 
Last edited:
Thanks for that.

I tried LLC, but even at just level 2, but idle vCore went from 1.36V to 1.44V, so I didn't even try to stress test it, fearing where vCore might end up!

This machine is without LLC manual tweaks currently idles at 1.36V with the cores at between 4.6 and 4.9GHz - 100x49 multiplier. At that setup, Cinebench puts all cores at 1.28V at 4.9GHz solid and reliable.

The machine will happily run reliably at 5GHz (CPU is delidded and binned at 5GHz and will actually run stable at 5.1GHz), but then vCore goes to 1.425V at load, and peaks at 1.44V at idle - that's idle with all power saving features disabled on the CPU.

Prime95 Max Heat test slows all cores to 4.6GHz at 1.264V vCore. I'd like it if I could get this to 4.9GHz without the drop to 4.6GHz. Considering that LLC seems to push the voltages beyond what I am comfortable with, are there any other things I could do to get the full consistent 4.9GHz, but without the 1.44V worry?
 
Jumper118 said:
running prime 95 dropping clocks will be because you are using avx version of prime 95 and the bios will have an avx offset of -3 in the bios because avx instructions sets run intel cpu stupidly hot.

you should be using the settings in the thread that they provided, not the auto oc function of the motherboard. you may fine it does need 1.425v to be stable, i could be fine at 1.35v or something.
Click to expand...

Aha. OK that explains the drop then - learning all the time here! :-)

You say "you should be using the settings in the thread that they provided,". Which thread? Who provided? Did I miss something?
 
Oh really. No idea about that. No information with the 8-Pack CPU I bought. I'll have a look.

How am I supposed to know the document it online if they don't mention it? Doh.

My CPU came in a box with a handwritten -6C on it. Does that mean something significant?

Ta
 
Would that still be relevant as I only bought the delidded CPU off 8-pack, and not the mobo?

I'm using an Asus Prime Z370-A mobo.

I'm confused by the various options.

I have "One-click" overclock from normal to Fast to Extreme.

And elsewhere I see an option to Load a 5GHz profile.

Is the Load option more targeted than the One-Click?
 
Perhaps you could answer the actual query I made instead of dissing my request.

In your 8700K delid video you say up to 1.425V is fine. My CPU is showing 1.44V at 5GHz and as a beginner at overclocking I want to know if that is safe, and if not what should I be adjusting so I don't fry my CPU.
 
Thanks for that list. Appreciated. Lot's to learn here.

Just one final question. You mention 3200 memory, but mine is:

32GB (2x16GB) Corsair DDR4 Vengeance LED, PC4-21300 (2666), Non-ECC Unbuffered, CAS 16-18-18-35, White LED, XMP2.0, 1.2V

Do your settings "For 3200mems io 1.05-1.1, sa 1.1, cpu standby 1.1." still apply for my memory?

Cheers,
 
OK I set the machine up with 8-pack settings, and it is stable and running fine.

DRAM Voltage at 1.40 showed up as red in the BIOS. Is that OK? Standards was 1.201V
 
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