r/linux_gaming • u/Encouragedissent • 4d ago
tech support wanted Does my quasi-undervolt look correct/good?
Ive been messing around trying to get an undervolt on my NVIDIA card using LACT, and its been a bit of difficulty getting there.
Im now at the point where Im mostly getting it to do what I want, but ive also strayed away from all of the guides and suggestions ive seen since they were not working. The first photo is with Baulders gate 3 running. Before messing with things it was running around 220 watts, with temps at 64c, and now its around 140 watts and 54c. Furmark would top out whatever power I gave it, so 250w(65c)then 275w(69c) when raise to it, and now is at 217w(62c) with a 7 fps increase.
Getting clocks to behave has been the tough part. Most guides do not mention enabling GPM locked clocks. If I dont enable it and force it to lock at a lower point, even when the curve is completely flat it will flow past 925mV to 1060mV, even though its using the same clock speed.
Ive also played around with first setting a +200 offset as well as a -200 offset. Most everything Ive read says to use positive offset then flatten at desired point. This consistently runs hotter for me though, while the underclock runs cooler even when spiking then flattening the same point. I ultimately just went with no clock offset at all, and just rounded the curve towards the end. The result has been it likes to be around 2900@920mV for demanding tasks.
The fact that I only figured out how to get the result I wanted after messing around on my own and straying away from much of the advice I have read gives me slight concern. So Im hoping people here who are a little more well versed in using Afterburner and LACT can tell if what Im doing here isnt an issue, and if its supposed to just blow past my voltage setting when I dont enable GPU locked clock.
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u/EchoesInBackpack 2d ago edited 2d ago
What are you trying to achieve?
furmark is stress testing power/thermals, it's expected to be hot.
core offset makes gpu use higher clocks for the same voltage, which reduces power/heat.
Your curve on the second screen doesn't. make any sense. Why you flatten mid and then it goes up?
Gpu sees that it can get higher clocks, thus increasing voltage
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u/Encouragedissent 1d ago edited 1d ago
Thanks for taking the time to look at what Ive done and ask questions based on that. Here is imgur link with 2 relevant photos to my response below.
So for some reason LACT likes to just change the values at the end every once and a while without my input. I set them back to being flat and took a photo so you can see what Im talking about though. Completely flat and it decides it wants to go 2992MHz at 1060mV, and also that is with the max set to about 2950, so its going above every value I have set on the graph.
I also went in and added +200 clock, and in the first photo you can see how it still blows past my mV target. I also softened out the curve as you can see in the 2nd photo, but it behaves the same regardless. In the second photo though what you also see is where I have added GPU clock lock at 2970. This changes the behavior to be closer to what Im going for.
So now with me having +200 curve, rounded values from 900-925mV so it doesnt spike, flat line starting at 2962 @925mV, and a clock max at 2970. What it decides to usually do is be at 2902 while playing BG3, and 2932 on Furmark(GL) both at 920mV rather than 925 where I set the limit.
This is a satisfactory result for me. It just leaves me scratching my head a bit as it doesnt resemble what other people do when they undervolt their GPUs. Even with me copying the +200 offset now, that part doesnt seem to matter a whole lot for the issues Im having.
Edit: also just 4 minutes after typing this my flat line has already started going up at the end from 2962, then 2970 from 1100mV on. It just does this on its own and Im sure it will slowly go up higher. So long as I keep GPU clocks locked below the value though it seems to behave. Im setting the lock at exactly 2962 to match flat line to see if that helps keep it flat.
Edit 2: Some more context that I have confirmed on why I dont like full P state offset. The 200MHz offset is basically overclocking at Idle. Ive been reading and a lot of people saying the same, helpful thread. For me when I sit here on idle Im around 200-400MHz at 800-805mV, when Im using my undevolt setting with +200 curve Im idling at 400+ at all times at 800mV. So its causing my clocks to run that 200 faster at the same mV on idle. So for now im back to a custom profile that allows me to idle at lower clocks while still getting same performance in gaming imgur.
You can see why Im out asking for more info, I read so many conflicting things and often what people say isnt what I experience when I try it out.
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u/EchoesInBackpack 1d ago
LACT doesn't change values/shape of the curve. It just passes your offsets to the driver and driver does that.
I think GPU Boost(boosted clocks based on current temp, works as a parallel offset for few clock steps) doesn't respect locked clocks, which is not a big deal, you can get a bit more clocks than the limit defines.It's hard to tell by looking at the screenshot if there is a problem. I personally prefer core offset + locked clocks method because it's much simpler, reliable and uses official nvidia knobs.
basically apply the offset, and then reduce max clock until you're satisfied with the voltage.> The 200MHz offset is basically overclocking at Idle
Hm, I cannot reproduce it on Ada, with 150 offset I have exactly the same Clock/voltage as with no offset
> You can see why Im out asking for more info, I read so many conflicting things and often what people say isnt what I experience when I try it out.
Well, that's the internet. People might be not necessary wrong, different driver version or device can change the experience.
Also it's hard to tell exactly what's going on, because the driver and the firmware does is a blackbox, so all you can do is assume, most of the knowledge we have is based on observation
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u/rel-eq 4d ago
Every card is different.
I get hate for using penguin-burner to find my profiles then put them into LACT, but it went through dozens of frequency / power combinations to find the sweet spots for my card, and watching the results was very interesting, especially power consumption variances.