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post #15 of (permalink) Old 05-15-2020, 06:24 AM
ncpneto
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Quote: Originally Posted by Falkentyne View Post
1.335v at idle is nothing because the amps draw at 1.335v is extremely low at idle (with LLC5/LLC High that's probably actually 1.320v-1.325v at idle as there is vdroop even at idle). Fully safe (even safer with lower LLC's!). Now if you were pulling 193 amps at 1.335v load (Measured via CPU on-die differential sense), you will degrade that processor (plus it would be completely uncoolable as well).

While 1.7v idle will slowly burn up your processor for sure, your processor is safe as long as you respect Intel's amps/voltage curve. (the problem is Loadline Calibration skews the entire formula because Intel doesn't design for Loadline calibration, only for AC Loadline (max 1.6 Ohms).

I don't believe that VRM Loadline is even mentioned in the Intel specification documents, only AC Loadline (CPU power supply) and DC Loadline (Power measurements). VRM Loadline is what is set by Loadline Calibration. It mentions that a lower AC Loadline will improve on current and temps (this will reduce the load voltage).

To stay in design limits, VRM input voltage must not exceed 1.520v, and VRM current (Amps) must not exceed 193 amps on 8 core CFL, and AC Loadline set to maximum of 1.6 mOhms. All of this assumes NO loadline calibration is being used. The 1.520v value is important because the VRM actually receives this input voltage on higher processor speeds/AC Loadlines when using AUTO voltage. Vdroop is what saves you.

The formula is basically this, with resistance being your loadline value (VRM loadline). While AC and DC loadlines are also in resistances, they are not used in the formula.

1520(mv) - (Amps * resistance)=maximum safe voltage your CPU should not exceed.
so at 193 amps, that's 1520 - (193 * 1.6)= 1.213v
At 150 amps that's 1520 - (150 * 1.6)= 1.280v
Thank you very much for your explanation. Finally, this LLC issue is becoming clearer to me!

Just to see if I am in the right understanding... currently my configuration is as follows:

9900ks
core: 51x
uncore: 48x
LLC 4
Adaptive 1.360v
(Asus Maximus XI Formula - LLC 1-8)

My load voltage is 1.181v on Prime95 (FFTs 12k and without AVX), and pulls 133A.

Therefore, according to the formula, the maximum safe voltage would be:

1.520 - (133 * 1.6) = 1.307v

Please, now my question is:
Would this be the maximum safe voltage at full load or the maximum configured in the BIOS?
Should I raise the LLC to 5 and lower the BIOS voltage to a maximum of 1,307 !? Or am I fine at 1.360v @ LLC 4?!

Thank you for your help!
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