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8700K - Fluctuating core speeds at idle when OC'ed?

Lysrin

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This question is part overclocking, part troubleshooting, but I thought a little more the latter so asking it here.

I've been playing around with the new 8700K, and allowed ASUS AI Suite 3 to do an automatic overclock. Took it to 4.9 GHz without any tweaking by me. But I do need to check what it's doing with voltages as I know the auto ones can be too aggressive on that, or so I read.

But I noticed something that seems odd: when idling the voltage and core speeds are fluctuating all over the place, observed in HWMonitor and CPU-Z. They only stay at a given speed for a few seconds and range from 0.8 to 4.6 GHz, from visual inspection.

I did try changing the Windows power management from balanced to high, no difference.

Quick searching last night suggesting that setting the voltage manually might be the solution, but didn't seem conclusive, only suggested. Haven't tried that yet.

I realised I'm not sure if it was doing this behaviour at stock clocks and settings so I will check that too.

Just wondered if anyone has seen this before? Known 8700K thing or artifact of auto-overclock perhaps?

If I wasn't monitoring I wouldn't have noticed. Neither PC performance nor cooling is impacted, just seemed like odd behaviour.
 

sswilson

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AFAIK all recent processors do this. I suspect it's a function of the power saving features.
 

JD

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If you disable SpeedStep and C1E support, that would lock it at the "maximum base" frequency but I think it would also disable the "turbo" functionality.
 

Lysrin

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OK, thanks guys. I'll do some research on SpeedStep and C1E support so I understand what is going on there. If it is normal for a recent processor then I can let it be and not worry about it.

If you are overclocked to 4.9, 4.9 is the turbo or boost speed, is that correct? So if turbo end up being disabled, does your CPU become locked to some lower frequency, even if overclocked?

I'll be honest, I haven't dug into OC'ing since my i7 920 days, just letting ASUS give me a little boost on my 4790K. If the answer to that question is "Just Google it!" I'm OK with that, but you guys are often more interesting than Google! ;)
 

enaberif

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OK, thanks guys. I'll do some research on SpeedStep and C1E support so I understand what is going on there. If it is normal for a recent processor then I can let it be and not worry about it.

If you are overclocked to 4.9, 4.9 is the turbo or boost speed, is that correct? So if turbo end up being disabled, does your CPU become locked to some lower frequency, even if overclocked?

I'll be honest, I haven't dug into OC'ing since my i7 920 days, just letting ASUS give me a little boost on my 4790K. If the answer to that question is "Just Google it!" I'm OK with that, but you guys are often more interesting than Google! ;)
The answer is... its fine lol.
 

JD

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When all cores are fully loaded does it remain at 4.9 or drop down a bit? Usually the turbo speed is a bit higher when only some cores are loaded. Then there's the AVX offset too... if your running AVX workloads then it (typically) drops the multiplier even lower.

But yes, it's fine. Better to have it drop the multiplier and voltages at idle, saves you power, heat and increases the lifespan of the chip and the motherboard.
 

Vittra

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It's actually changing much faster than what you see being reported, especially if you are reviewing those speed changes in the Asus Suite.

Here's an indepth article of what Speed Shift is actually doing as of Skylake:

https://www.anandtech.com/show/9751/examining-intel-skylake-speed-shift-more-responsive-processors

Here's an update of the tweaks done as of Kaby Lake which holds true through to Coffee Lake:

https://www.anandtech.com/show/10610/intel-announces-7th-gen-kaby-lake-14nm-plus-six-notebook-skus-desktop-coming-in-january/4
 
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Lysrin

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Thanks for the links Vittra!

It's just looks weird when it is sitting at 799 MHz, 0.68v, and then right up to 3000 or 4500 MHz and 1.26v for a half second or so and back. But if it's fine, that's cool. I just leave it and read up on the tech itself to understand it better.

JD, running Prime95 v26.6 (small FFT torture test) looks like it can actually only get all cores to 4.8 GHz at slight above or slightly below 1.25v. Depending on which program you check it shows 4.76 to 4.802. Temps get to 88C on one core, 79-88C across all cores after about 5-10 min of Prime95. I'm guessing when I let ASUS Suite do the overclock the default set up was per core rather than all cores, so the 4.9 was only reached on one.

I'm OK though with a fairly low voltage (isn't 1.25 fairly low? I've seen some people going as high as 1.4 to get 5 GHz) running all cores at 4.8. That seems pretty good doesn't it?
 

rjbarker

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You should consider playing around with OC'ing without the AI Suite...do it manually....theo ne thing I dont like with those "Auto Overclock" functions is I have no idea what voltages or what changes are being made in the BIOS......
.....you get more "intimate" with our BIOS / UEFI going manual.....hop on over to ROG Forum as you have an ROG Board...great OC'ing tutorials ...even youtube tutorials....Manual OC'ing is pretty straight forward now...only a few settings to change......
 

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