Help me understand core voltages (8700k)

Tris1066 · 14 Mar 2018 at 12:33

I'll admit, I'm a massive noob when it comes to OCing CPUs...

I followed a guide on OCing my 8700k, got it running stable and reasonably cool at 5GHz with 1.26v (set in bios). Temps were generally 30 degrees while idle, 50 degrees while gaming and 70-75 under avx loads while stress testing. (I'm cooling with a 240mm aio)

What baffles me is that when I look at the core voltages (via intel xtu), the CPU is idling at 1.362v, dropping to 1.30v when under load, and, most worrying, I see split second spikes to 1.47v while avx stress testing!

Seeing 1.47v freaked me out enough that I've dropped everything back to stock speeds.

Why on earth is it running so much higher than the value I set in the bios?

Awahwah · 14 Mar 2018 at 12:52

How have you set the voltage, manual/offset or adaptive? 1.26v seems low unless you have a very good chip.

Tris1066 · 14 Mar 2018 at 13:00

Awahwah said:
How have you set the voltage, manual/offset or adaptive? 1.26v seems low unless you have a very good chip.

I suspect it's adaptive (although I didn't see any specific option in the bios for either adaptive or manual). I just changed the entry for "CPU VCore".

I pretty much followed this guide (https://www.google.co.uk/amp/s/overclocking.guide/gigabyte-z370-overclocking-coffee-lake/amp/) to the letter and dropped the voltage a bit when it was stable at the starting point of 1.28v.

Edit.. may have stumbled across my answer... There's settings called IA/AC and IA/DC under the "internal VR controls" menu, setting these to "1" seems to disable the pre-programmed SVID which is whats giving my voltages a mind of their own.

Awahwah · 14 Mar 2018 at 14:56

IA/AC and IA/DC if you use Adaptive are needed, for my board I set to .01 for both. I made the mistake of not changing it once and saw 1.5v in the bios - changed it very quickly.

Tris1066 · 14 Mar 2018 at 23:20

Well, I've set my IA/AC and IA/DC to 1 (which is the gigabyte equivalent of 0.01 in other bios's) and it gets even more baffling...

My voltage now remains much more stable, I set the VCore a bit higher, expecting that my previous 1.26v was a bit low, I went for 1.3v... now intel xtu tells me that I'm idling at 1.230v and under non avx loads im stable at 1.229v, rising to 1.24v under avx stress testing.. my temps are roughly the same as before.

Beginning to think I've got a faulty sensor as I've never heard of a non delidded 8700k being 5ghz stable at 1.24v!

***Edit, okay, it wasn't a faulty sensor, it was a faulty user! The VCore reading in intel xtu is actually showing the VID, looking at hwinfo64 (when I look at the right bit) shows me that I was indeed getting 1.3v (1.308v to be precise).

Just for a laugh I tried for a 5.2GHz OC, at 1.38v it was stable but a bit toasty (90 degrees), dropped back to 5GHz at 1.3v. Much happier now my voltages are making sense, and matching up with other 8700k users results