Comparing undervolt vs PPT-limit vs fixed clock on ryzen 3600

[Cowboystrekk]

I wanted to compare performance, temps and consumption between the 3:
Cinebench15:
Stock: 193s/1545m 3925MHz 66C 90W
-36mv UV: 193s/1560m 3950MHz 65C 90W
65W PPT: 193s/1480m 3750MHz 54C 67W
3.8GHz@1.035V: 178s/1510m 51C 60W
3.9GHz@1.09V: 183s/1550m 54C 64W
4.0GHz@1.135V: 188s/1590m 55C 70W

Ran CB15 5 times on multiscore and found avg of score, temp and consumption.

Idle consumption with ryzen balanced is 18-20W on all different setups. Undervolts of more than - 36mv negatively affected score.

Tested SOTTR and only the fixed 3.8GHz@1.035V gave a slight reduction in CPU render score of 1% lower than other results.

Take-away message? PPT-limit or fixed clock at low voltage will have a very large impact on temps and consumption, PPT-limit will slightly lower multitreadscore but not affect singlecore perf, while fixed clock at low voltage does the opposite (3.9GHz). Fixed clock at low voltage fuxed the idle-temp jumps. At all other settings idle temp jumps between 31C to 48C due to volts/amps jumping around, at fixed clock it stays at 31-35C.

 

[Cowboystrekk]

Was supposed to say 178s on 3.8GHz@1.045V

 

[londiste]

Cinebench R15 is quite good CPU benchmark in a way that it pretty much tests CPU only and scales linearly with clock speed.

For this CPU:
- Per GHz it gets ST score of 47:
Stock, UV and 65W PPT run ST at 4.1GHz
- Per GHz it gets MT score of 397.5 - 8.46x ST, putting SMT efficiency at 41% which is pretty good:
Stock and UV run at around 3.9 GHz (stock probably mostly at 3875Mhz and UV at 3925MHz) and 65W PPT runs at 3700-3725MHz

In terms of power efficiency (MT score per W):
- 3.8@1.035V: 25,2
- 3.9@1.09V: 24,2
- 4.0@1.135V: 22,7
- 65W PPT: 22,1
- UV: 17,3
- Stock: 17,2
I am quite sure the best perf/W is below these frequencies for Zen2, I would assume between 3.2 and 3.5GHz.
Manual voltage adjustment obviously helps with efficiency for these fixed frequencies settings.

 

[Cowboystrekk]

I tested a bit lower as well, calculated points pr Watt:

3.6 0.98V 54W 26.5ppW
CB15 1430 49C

3.7 1.01V 56W 26.3ppW
CB15 1470 50C

To me it seems lik 3.7GHz@1.01V is the sweet spot since going below barely improves ppW.

Could be different on other ryzen 3000 that are better binned than mine

 

[londiste]

3.6GHz did not work with an even lower voltage?

Voltage reductions:
4.0 > 3.9: 45mV
3.9 > 3.8: 45mV
3.8 > 3.7: 35mV
3.7 > 3.6: 30mV

 

[Cowboystrekk]

3.6GHz did not work with an even lower voltage?

Voltage reductions:
4.0 > 3.9: 45mV
3.9 > 3.8: 45mV
3.8 > 3.7: 35mV
3.7 > 3.6: 30mV

Nope, tried 0.97V and 0.975V, became unstable quickly in CB15.

 

[Mussels]

I love PPT control on ryzen, sadly my 2700x drops as low as 3Ghz on 65W PPT

 

[Cowboystrekk]

I love PPT control on ryzen, sadly my 2700x drops as low as 3Ghz on 65W PPT

That was quite a drop. Sweetspot must be a bit higher than 65W PPT I guess?

 

[Mussels]

That was quite a drop. Sweetspot must be a bit higher than 65W PPT I guess?

around 90-110W, which is basically stock (105W)

 

[Cowboystrekk]

around 90-110W, which is basically stock (105W)

Seems like ryzen 2k and 3k behave very different then.