Undervolted AMD Ryzen 9 3900X shown be just 23% slower while drawing 36% less power at 1.00V Vcore

[Redaktion]

The AMD Ryzen 9 3900X was shown to suffer only a nominal performance hit while drawing significantly less power when undervolted to 1.00V. Interestingly, the clock speeds across all tested Vcore voltages remained the same at 4.2 GHz although there were perceivable differences in performance and power draw from the wall at different Vcore values in the Cinebench R20 benchmark.

https://www.notebookcheck.net/Undervolted-AMD-Ryzen-9-3900X-shown-be-just-23-slower-while-drawing-36-less-power-at-1-00V-Vcore.427867.0.html

[MrRobot]

No reason to buy a flagship CPU and cripple performance

[Vaidyanathan]

No reason to buy a flagship CPU and cripple performance

Yeah but this is more about trying to see how low of a voltage it can operate. Also, those with lower wattage PSUs might find some benefit with undervolting.

[mmc]

No reason to buy a flagship CPU and cripple performance

Tell that to laptop owners...

[SethNW]

There is one potentially more effective way with lower performance loss. And that is PPT, Package Power Tracking. You can set that to lower value and while CPU will manage itself, it tends to retain more performance. So it might be worth testing too.

[Not_anton]

Power consumption is "at wall", not "CPU"!
If we take a rated 105W for CPU at auto voltage, it means the rest of the system consumes 111W. And at 1.0V the CPU takes only 28W, a four times power reduction for 23% performance loss.

Could that be the key for 64-core Epycs at reasonable TDP?

[Matthew White]

Power consumption at 'Auto' was 216V while it dropped down by 35.6% to 139V at 1.00V Vcore.

Suppose to be 216 watts and 139 watts.

[not_anton]

Power consumption "at wall" includes the whole computer with CPU, chipset, memory, power loss in PSU, fans, etc. Undervolting affects only CPU.
Why would you compare a percentage voltage drop on CPU only with a percentage power drop of the whole desktop box with all other components not affected by CPU voltage?

[SystemBuilder]

This is GREAT work.  As past chair of the energy conservation committee at a large university, and as a computer scientist, I would LOVE to get a 12-core CPU but I would HATE to be wasting power with that CPU !!  You only need the 12 cores maybe 5% of the time you are using it!  The other 95% of the time, you can be nice(r) to our planet, mother earth.  You need less than 1/2 of a core for editing in Google Docs or MS-Word.

[Vaidyanathan]

Power consumption at 'Auto' was 216V while it dropped down by 35.6% to 139V at 1.00V Vcore.

Suppose to be 216 watts and 139 watts.

Thanks for spotting it. Corrected the error. :)

[Vaidyanathan]

This is GREAT work.  As past chair of the energy conservation committee at a large university, and as a computer scientist, I would LOVE to get a 12-core CPU but I would HATE to be wasting power with that CPU !!  You only need the 12 cores maybe 5% of the time you are using it!  The other 95% of the time, you can be nice(r) to our planet, mother earth.  You need less than 1/2 of a core for editing in Google Docs or MS-Word.

Yes. That's a good way of thinking especially when the energy savings are high. Undervolt it when not in stress and come back to baseline values when load is high. Doing it frequently might not be practical always but yeah, great use case.

[Jo Grey]

Interesting that they saw such a performance hit at 1.20v... not at all what I am getting out of my 3700x... I have found that the absolute best all around performance (factoring in heat and throttle limits) to be a manual overclock of 4.05ghz at only 1.125v (48w) with that I am hitting 4845 in cinebench R20 vs only about 4690 with voltage set to auto and PBO enabled, and I was routinely hitting the throttle limit and even once hit the 95c shutdown limit with auto and pbo, the manual undervolted OC keeps me at a nice 77c after about 5 consecutive cinebench runs and gives higher scores in both cinebench and 3dmark. Granted if I wasn't in a tiny mini-itx case I could use better cooling and overvolt instead of undervolt and probably hit a nice 4.2ghz across the board without the throttling issues.