falkentyne
8 points·
19 days ago·edited 19 days ago
Is your board a Maximus XI board (supports CPU differential on-die sense voltage monitoring) or a Gigabyte Z390 or other board with VR VOUT access and Amps (current monitoring or Current IOUT) monitoring in HWinfo64 ?
Maximum safe voltage electrical specification guidelines are based on:
- default VRM loadline (Intel specification of 1.6 mOhms) being respected as this is what the chips are designed for. Using a custom loadline calibration reduces the mOhms value (less mOhms=less vdroop) which will change the formula for what your processor is using, then you will have to match it to the "Intel" formula to compare.
- Amps limit being respected. (193 amps)
- Vcore / amps curve being respected.
This formula is based on Max VID=1.520v at 0 amps (no clock signal) under the following formula:
Max VID - (resistance * amps)= max safe live voltage, up to TJMAX.
where max VID is 1520mv (1.520v), max amps is 193 amps and resistance (Loadline or vdroop specification) is 1.6 mOhms. VID is in millivolts because resistance is in milliohms, thus the same units so no conversion is necessary in the math.
Total vdroop is amps * resistance.
1520 mv - (1.6 * amps) = max safe live voltage.
So you plug in how many amps you're pulling and then do the math.
Some quick values:
1520 - (1.6 * 193) = 1.213v.
1520 - (1.6 * 150) = 1.280v
1520 - (1.6 * 125) = 1.320v
1520 - (1.6 * 100) = 1.360v.
1520 - (1.6 * 75) = 1.400v.
And so on.
This is based on intel default loadline calibration and based on "Auto" Vcore and allowing the AC Loadline (NOT the same as VRM Loadline) to set the initial operating voltage, which is capped at 1.520v BEFORE VDROOP.
Also keep in mind these are MAXIMUM safe limits. This does not mean that you should run your processor 24/7 at the border and think it won't degrade any faster. While technically, you are still in Intel's specifications if you set a 1.520v bios voltage with INTEL DEFAULT loadline calibration (1.6 mOhms)--since there is going to be vdroop at idle, so the VR VOUT will never show 1.520v, is it really a good idea to have your IDLE voltage at absolute maximum before there is risk of damage? I don't think so!
Better to just set "Auto" Vcore and let AC Loadline and Thermal Velocity Boost control the input vcore then (with intel spec loadline calibration). TVB will reduce the base VID depending on temps as explained here:
https://rog.asus.com/forum/showthread.php?106375-MCE-explanations-and-others&highlight=explanations
That's why, at idle, with a max AC Loadline of 1.6 mOhms and a x50 multiplier and Intel spec Loadline calibration (LLC2 on Asus, "Standard" or "Normal" on Gigabyte Z390, your on-die sense vcore will be more like 1.41v rather than 1.48v (thanks to Thermal Velocity Boost !)
This 'initial operating voltage' is a complicated interaction between the "base CPU multiplier's original VID, Thermal Velocity Boost voltage optimizations, and AC Loadline mOhms value, where a higher ACLL will raise operating voltages. Max spec for ACLL is 1.6 mOhms--which is the same value as default "Vdroop" (VRM) loadline.
Using a custom LLC setting requires you to know how much vdroop is being reduced. For example, 50% vdroop reduction (e.g. -50% vdroop on eVGA Dark) is 0.8 mOhms (50% of 1.6). Asus Maximus XI LLC5 is also 50% reduced vdroop (0.8 mOhms) and Gigabyte's LLC High is 50% reduced vdroop.
LLC6 and "Turbo" LLC is 75% reduced vdroop, or 0.4 mOhms.
To calculate where you are in the safe voltage/amps curve on fixed manual vcore and custom LLC, you change the formula as such:
Bios set vcore - ( loadline calibration mOhms * CPU amps)= load cpu vcore (RMS) you are actually using.
For example:
1.340v Bios set and Loadline calibration: Turbo / LLC6, and pulling 150 amps:
1340 mv - (0.4 * 150) = 1280mv = 1.280v.
That means at 150 amps, 1.340v set in BIOS and 0.4 mOhms of loadline calibration, you are right at the max safe limit, and should be very careful about raising vcore without improving your cooling solution. (in this example, pulling less than 150 amps puts you below the safe limit, pulling more than 150 amps starts to put you beyond it).