Glad you’ve got it up and running, you’ll find it churns work out like a good’un.

Your temps are about the same as my 65 watt Ryzens using the stock cooler - changing to the 105 watt rated prism cooler dropped that by about 10c.

I undervolted my R5 3600 and it helped the temp without affecting performance but when I tried with the R7 3700x it flat refused to boot and I had to revert to standard. I’ve not tried on the R9 3900.

@Bryn Mawr

I concur with those who reckon the default CPU Core voltage is unnecessarily high for systems typically used to crunch BOINC projects! So, regarding your failed under-volting...

I have a 3700X on an Asus X470-F motherboard, and I'd been following debates about performance tuning that wasn't about overclocking, as I reckoned the default CPU voltage was too high. The system does both CPU and GPU work on various BOINC projects (but never uses more than 12 or 13 of the 16 available "CPUs" for BOINC stuff...)

I knocked about 5C off the running temperature of a fairly busy system [including GPU work] by reducing Package Power Tracking from the standard 88W to 80W. (That's higher than what it would set it to for "Eco Mode" and seemed like a reasonable thing to try...) As a side-effect, CPU Core voltage on a busy system went down from well over 1.3V to comfortably below 1.3V. There was no obvious drop in performance or throughput - clock rates and job times were within +/- 1% of the pre-change values (and yes, some of them seemed to run a little better at the reduced voltage!)

The above reflects the system running an Einstein@home GPU task as well as various CPU tasks - as I have an NVIDIA card, Einstein hammers a CPU as well as the GPU! If not running GPU work, the CPU seemed to run 10C..15C cooler and the motherboard temperature dropped by over 10C - CPU voltage was lower too. However, I was more interested in reducing power a little -- temperatures (even with ambient above 30C) were acceptable after the change...

I suspect that if one is trying to reduce power draw (rather than just improving cooling to reduce temperature) letting the system work out its own power curves is probably preferable to user tweaking, though judging by comments at Seti@home and elsewhere when the Ryzen 3xxx machines appeared, lots of folks have successfully under-volted. Could be it's down to what motherboard (and BIOS) one has (and, of course, what it will let you change!)

Cheers - Al.

On my Ryzen 3900x and Ryzen 2700x, I have Turbo core / Turbo boost off in Motherboard BIOS settings, to reduce CPU voltage and save some watts. The speed loss is almost nothing while all cores are maxed.

I found the best way to reduce CPU speed is to just keep the Motherboard BIOS settings at auto/default CPU frequency and auto CPU voltage, and adjust CPU power management in Windows/Linux. On Windows, edit power plan, maximum processor state. Can download a windows tool called HWinfo64 to see CPU voltage, temperature, frequency, and possibly more. Linux should have CPU frequency scaling tools and see results with lm-sensors. Frequency ajustments while in operating system can save time and can avoid any need to restart computer.

Here is my Maximum processor state (MaxPS) showing changes on HWinfo64 details.
Ryzen 2700x Win10, Asus Prime B350, Heatsink PureRock BeQuiet 150w TDP, turbo core off.
MaxPS, speed, CPU volts, CPU package power, CPU die average
100 % , 3.7 GHz, 1.156v, 97 w, 64 C
99-86%, 3.2 GHz, 0.950v, 60 w, 51 C
<= 85%, 2.2 GHz, 0.781v, 34 w, 41 C

Ryzen 3900x Win10, MSI B450 Tomahawk, stock Heatsink fan included in CPU package, turbo core off.
100%,3.80 GHz, 1.125v, 110 w, 82 C
99%, 3.73 GHz, 1.075v, 98 w, 77 C
98%, 3.68 GHz, 1.050v, 93 w, 73 C
97%, 3.63 GHz, 1.025v, 88 w, 70 C
96%, 3.60 GHz, 1.012v, 86 w, 69 C
95%, 3.58 GHz, 1.000v, 84 w, 68 C
94%, 3.53 GHz, 0.981v, 81 w, 67 C
93%, 3.50 GHz, 0.975v, 78 w, 65 C
92%, 3.45 GHz, 0.950v, 74 w, 64 C
91%, 3.40 GHz, 0.938v, 72 w, 63 C
90%, 3.38 GHz, 0.938v, 72 w, 63 C
... didn't feel like testing all speeds ...
<59%,2.20 GHz, 0.925v, 56 w, 55 C

Ryzen 3900x have nice frequency adjustments from Windows maximum processor states. It is amazing how much watts is saved with slightly less GHz speed, while BOINC use all CPU threads.

You should find that goes up some over the next couple of days.

The default BIOS was set to 3800 Mhz and 1.4nn volts

I changed BCLK Frequency from 100.00 to 98.00 and got back to the BIOS after a boot and it was down to 37nn Mhz and still 1.4nn volts. Figured that must be wrong.

There are too many parameters in all that BIOS which I don't understand. My instincts tell me to only make changes I understand. I was about to put it all back to default and give up when I noticed something about auto tuner in their "AI". This was not in the manual. Gave it a try and checked the settings after a boot: 4000 Mhz and 1.2nn volts.

Well that was exactly what the you suggested so I gave it a go. The temp now hovers at around 70-72 instead of 76-79.

Now to see if the output changes much