Ryzen 3600 power scaling

porina · September 28, 2019

I probably could make a pretty chart with the above but I've lost motivation now I got some data. Thought I'd post anyway.

Key components:

Ryzen 3600 stock settings apart from PPT, adjusted as described below.

Asrock B450 gaming ITX/ac bios 3.50 (1.0.0.3ABB)

Noctua D9L with two alternate fans

PSU is unknown without taking apart the system, but is likely one of Corsair CX450M, CX550M, or CX450.

Crucial Ballistix 2666 2x4GB

Test methodology is to run Prime95 29.8b6 as load, set to stress test with 6 threads each running 128k FFT in place. This configuration is not sensitive to ram speed. Using Ryzen Master, I can adjust PPT value to lowest allowed of 44W, to default stock value of 88W, and beyond. I started at 44W, and left it running for at least 5 minutes. At that point, I reset hwinfo64 and allowed that to take readings for at least one more minute. The average reading for clock, CPU temperature, and VID were noted. Note there were 6 readings for clock and VID, so I had to kinda average by eyeball to get a single number. Wall power was manually read separately. PPT was increased to the next level and this was repeated. Set at 88W PPT, it was stuck at 100%, but at 99W set, it dropped to 90% PPT. I had reached its limit so I didn't take measurement past 88W.

In short, nothing of great surprise here. Lower power at the CPU translates to lower performance, but the drop in clock is much less than the drop in power, so efficiency goes up. Looking at the system as a whole, the power drop is less than just for the CPU as we have other things using power other than just the CPU. This dilutes the savings a bit, but there is still an overall efficiency gain from lowering CPU power. This is in part why I think lower clock versions of the 3900 and 3950, maybe even TR3K would be pretty interesting from a performance efficiency standpoint, even if they don't have the highest clockspeeds.

As a follow up test, I'd like to do this with a better cooler on the CPU. I suspect it would boost to higher clocks at each power level, but the question is how much?