Thursday, April 13, 2017

Some Ryzen power draw data

Ok so I finally have a operational Ryzen system and while the BCLK controls in the BIOS are being stupid I can still do other testing so here is that other testing.

The goal of this data is to figure out how the power draw of Ryzen is split between the cores and everything else like the SOC. For my testing I'm using Asrock's X370 Taichi and a Ryzen 7 1700. I'm not 100% sure how the 12V of the single 8pin CPU power connector is distributed but for the most part it doesn't matter because the focus here is figuring out core power draw in order to be able to gauge Vcore VRM requirements for overclocking.

So here is the data! Do note it is rather rough as far as error margin goes because CPU temperature was not maintained across test runs and higher temperatures do lead to elevated power draw. I didn't bother with more accurate measurement methods because chip to chip variance will cause larger power draw discrepancies than my measurement methods for this data.

Clock Voltage Core Config Power Draw
3.95Ghz 1.45V 4+4 170W
3.95Ghz 1.45V 3+3 135W
3.95Ghz 1.45V 2+2 100W
3.95Ghz 1.45V 1+1 60W
3.95Ghz 1.45V 4+0 100W
3.95Ghz 1.45V 3+0 75W
3.95Ghz 1.45V 2+0 65W
All tests were done with SMT turned on.

From this we can see that 1 core with SMT at 3.95GHz 1.45V consumes roughly 17W. The other things hooked to the 8pin connector pull a constant 30W. I suspect that most of this 30W would be the SOC portion of a Ryzen CPU.

This means that for an 8 core Ryzen chip Vcore current draw at 4Ghz/1.45V is only about 96A. 6 core CPUs would be about 72A and 4 cores only about 48A. Basically that means the Vcore VRM current through put required for your motherboard to not go up in flames is absolutely minuscule. Basically any AM4 motherboard should be capable of doing 4Ghz or more on 6 core CPUs. Motherboards with good 4 phase VRM designs should also have no issue pushing 4Ghz on 8 core CPUs.

Now of course this is only looking at current capability. Better VRMs also have better voltage regulation as well as current through put which means that they may clock a little better for any given voltage just because it won't fluctuate as much as it does on weaker VRMs. However it does mean that for daily OCs you really don't need the insane VRMs that come on boards like the Gigabyte Gaming K7, Asrock X370 Taichi/Professional Gaming or Asus Crosshair 6 Hero.

Also thanks to all the Patreons and shirt buyers for making this article possible!

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