Increasing LLC vs increasing Vcore

Incognito Clown · March 15, 2019

I recently bought a i9 9900k cpu which should according to Intel's spec run at 1.39 volt. This is therefor also the core voltage (vCore) that was set by default, in the bios of my Gigabyte Aorus z390 Ultra motherboard.

Like pretty much every chip, my i9 can actually run stock speeds at much less voltage. I've set the vCore in my bios to 1.26 volts, which seems stable (no hard or soft WHEA errors yet).

Although the VRM does supply 1.25 volts when idle, it only supplies 1.14 to 1.17 volts under full synthetic load (for example during an AIDA64 system stability test).

At first I thought my VRM was misbehaving, but I quickly found out that this is expected behavior and is called Vdroop.

It seems to be a feature that lowers the average core voltage during load, to reduce voltages spikes when switching between idle and load which could otherwise damage the CPU. (correct me if I'm wrong)

However, dropping over 0.1 volt (idle -> load) seems huge to me. Is it?

I've also seen people talking about Load Line Calibration, or LLC for short. This is a feature most motherboards support, which can reduce the just mentioned Vdroop.

What is usually better: Higher Vcore setting without touching the LLC, or a lower Vcore setting and an increased LLC level?

And if I'm seeing 0.1V differences between idle and load scenario's, would it then be recommended to increase the LLC level?

Also a little side question; if (professional) overclockers are talking about "we did x ghz at x volt" do they usually talk at the actual voltage during loads? Or the voltage that is applied in the bios?
I did see a video of someone from Optimum Tech who said that probably every i9 could run stocks between 1.15 and 1.25 volts. I did have to enter 1.26 volts in the bios, but it actually runs at 1.55 on average during loads. Am I having a good or a bad silicon chip here?

KarathKasun · March 15, 2019

VDroop is just a side effect of increased load. In any electrical system, voltage drops as you increase amperage. Primarily this is due to the innate resistance of conductors. Its not a feature.

LLC should be set to minimize droop while also minimizing overshoot. I would say that LLC should be increased to the point where droop is less than 10% but not less than 5%. With 1.4v, droop should be 0.05v - 0.07v. At 1.2v it should be 0.04v to 0.06v.