AMD 9900X Undervolted and the results.

[wade7575]

I built an AMD based system when the ASUS X870E ProArt mobo was released and I planned on undervolting the CPU to get it to run cooler all along as I like my CPU's to run cooler if I can and not killing the performance completely,these are the results and what I did.

System Specs ASUS X870E ProArt Mobo
CPU AMD 9900X 12 Core
G.Skill Flare X5 6000mt 32GB
Intel ARC A580
Seasonsonic 1000Watt PSU
Noctua NH-D15 G2 newer version CPU Cooler

I was first told by a guy that I could just go into PBO and go to all cores and start lowering the voltage of the cores until my system ran unstable then give it back some voltage and I'd be able to watch the temps drop like magic,he also said to leave the boost clock max speed at 5.6ghz and it would still boost that high well lets just say that method was a complete flop and did nothing at all to drop temps or to reduce voltage going to the cores.

What I ended up doing was to change the PPT EDC TDC limits and use Curve Shaper and Curve Optimizer the stock settings for the 9900X are below.
PPT 162W
TDC 120A
EDC 180A


These are my custom bios settings.
PPT 130W
TDC 105A
EDC 120A

I went into Curve Shaper and for the Medium Part of the Curve I applied Negative 15 to all 3 points of the curve,for th High part of the curve I applied Negative 20 for all 3 points of that curve,I then went into Curve Optimizer and applied negative 10 to All Cores. and EXPO1 Enabled.


What I did was use HWInfo and start with these settings below which were suggested to me and raised the numbers slowly.
PPT 88W
TDC 75A
EDC 150A

I watched the PPT/TDC/EDC numbers with HWInfo and when I settled on 130W for the PPT I then watched the EDC/TDC more closely and I set them so they were at 80% maxed out when running Handbrake as to leave a bit of headroom.

With stock bios settings and EXPO1 enabled and running Handbrake I was getting temps of 70C to 71C.

Encoding a .265 file I got 643FPS and Encoding H.264 1108FPS

With my custom bios settings I got 51C to 55C

Encoding a .265 file I got 618FPS and Encoding H.264 1083FPS

I'm pretty happy with the results because the encoding to it takes to encode the same file with stock or my custom bios settings is pretty much the same and vary by 5 to 7 seconds but the best part is I shaved off 16C from my CPU temps.

I wasn't sure what to expect before I purchased my system and I thought with air cooling maybe I can drop 5 to 7C maybe even 10C but didn't think I would be able to drop 16C with almost no loss in performance.

I know these CPU's are meant to run at 70 or even 78C but I didn't want to being running in the winter at 71C and in the summer at 80C or higher so I wanted to try and drop my temps,I feel the trade off of giving up almost no speed to the point you don't even notice it and to drop 16C is well worth it.

 

[EarthDog]

Thanks for sharing! Good stuff!

and I set them so they were at 80% maxed out when running Handbrake as to leave a bit of headroom.

So, you lowered wattage, then lopped off another 20% on top of it?? And you lost 4% and 2%??? Not bad!

I know these CPU's are meant to run at 70 or even 78C but I didn't want to being running in the winter at 71C and in the summer at 80C or higher so I wanted to try and drop my temps,

I know you want it to run cooler, but be aware that these CPUs are intended to run well into the 90s and will live a long, healthy life this way.

 

[freeagent]

You should measure GFlops using Linpack Xtreme

 

[wade7575]

Thanks for sharing! Good stuff!


So, you lowered wattage, then lopped off another 20% on top of it?? And you lost 4% and 2%??? Not bad!


I know you want it to run cooler, but be aware that these CPUs are intended to run well into the 90s and will live a long, healthy life this way.

I just don't trust the heat factor when they claim they will last along time running at 90C,it one of those thing where I don't it to like my CPU fails because of it then they all start failing and it's because heat then AMD comes out and says ya and about that being designed to run 90C all day long we got that wrong bigtime.

 

[EarthDog]

I mean, things happen, you can't ride or die on one offs... at least, I can't. Besides, that's what the warranty is for.

Please don't misunderstand me, cooler is better, i get it. But when I buy something I want to get the most out it, as opposed to intentionally slowing it down, even a few %, based on arbitrary values.

The good news is we all get to do what we want, regardless of some internet blow hards (me, lol).

 

[The Coolest]

Like any other modern chip, there's really no longevity problems with running the CPU close to Tjmax.
The PBO method is decent at squeezing some extra performance if you have the thermal headroom, as it relaxes/removes the power limits.
Temperature or FMax (override-able) will be your limiting factor with PBO enabled.
You could combine PBO with undervolting to gain performance over stock at similar thermal/power levels.

I still think it's pretty cool what you did, though. Tweaking the chip to provide similar performance at much lower power figures and lower temps.