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How far down can you downvolt the rtx 4090?

deama

deama

deama

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5 Jul 2020
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So I'd like to get the best GPU money can buy, but I hate how much power it uses, and out of principle, I would not like to use a GPU above 200W.

So I was wondering if you can just downvolt it to around 200W? Is it possible? I heard at some point it starts stuttering if you set it too low with the power limit option, and someone else said it has a limit of 300W with voltage curve.

Anyone tried going down that low without any weird issues etc...?
 
Undervolting like overclocking suffers from diminishing returns, I suspect 200w is well below optimal. The video from tech yes is pretty good on this subject.
 
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ToOo said:
Undervolting like overclocking suffers from diminishing returns, I suspect 200w is well below optimal. The video from tech yes is pretty good on this subject.
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Yes I watched that one, but what I'm interested is whether the card can even go down to 200W without getting any weird stutter issues or whatnot.
I'm fine with lower performance, just don't want stuttering issues or weird stuff happening with the GPU.
 
At 50% power limit the boost algorithm probably doesnt have enough room to manuver since the GPU will need a minimum voltage (probably 0.7V) to function correctly. Normally the boost algorithm can adjust the voltage and frequency to meet the power target, but since you would set the power target so much lower than is normally expected there is very little if any of the boost curve allocated to that performance region, hence the odd behaviour.

Probably the best bet to make this work is with a fixed clock, this is done by locking the voltage in the curve editor and then testing for the highest stable frequency at that voltage. With this method you dont actually set the power target.

I dont have a 4090 so cant give you an direct example, but this is roughly what you are proposing looks like on an Ampere 3090 .


P5BBrSa.png
 
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ToOo said:
At 50% power limit the boost algorithm probably doesnt have enough room to manuver since the GPU will need a minimum voltage (probably 0.7V) to function correctly. Normally the boost algorithm can adjust the voltage and frequency to meet the power target, but since you would set the power target so much lower than is normally expected there is very little if any of the boost curve allocated to that performance region, hence the odd behaviour.

Probably the best bet to make this work is with a fixed clock, this is done by locking the voltage in the curve editor and then testing for the highest stable frequency at that voltage. With this method you dont actually set the power target.

I dont have a 4090 so cant give you an direct example, but this is roughly what you are proposing looks like on an Ampere 3090 .


P5BBrSa.png
Click to expand...
Yeah that's what the guy on the video said and what I was thinking of doing. Problem is though I donno if I can go down that low, I heard you can't and it's capped in the BIOS of the GPU?
 
CuriousTomCat said:
I wonder if a 200w 4090 would still be faster than a 4080
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Let's estimate it: Assuming that power is proportional to the cube of performance, then a 200W 4090 would be (200/450)^(1/3) = 0.76x as fast as a stock 4090. And if we assume that performance scales linearly with cores and clock speed, then the 4080 should be (9728/16384) * (2505/2520) = 0.59x as fast as a stock 4090. Thus one would expect a 200W 4090 to be faster than a stock 4080.
 
VincentHanna said:
What's the point? It's like saying I bought a Bugatti Chiron Super Sport 300+ but I don't like wasting petrol so I drive at 10 mph everywhere.
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I just want the best performance I can get at 200W, so I thought buying the best card and just downvolting it would do the trick, because buying e.g. a 4080 and downvolting it to 200W would probably give worse performance than 4090 at 200W.
 
deama said:
So I'd like to get the best GPU money can buy, but I hate how much power it uses, and out of principle, I would not like to use a GPU above 200W.

So I was wondering if you can just downvolt it to around 200W? Is it possible? I heard at some point it starts stuttering if you set it too low with the power limit option, and someone else said it has a limit of 300W with voltage curve.

Anyone tried going down that low without any weird issues etc...?
Click to expand...
You barely need to worry about such things. Most games go over 120fps at 4k. Set a frame cap limit in Nvidia control panel and you're 300w in most games. Then when you need extra power for the games where it can scale up.
 
XeNoNF50 said:
You barely need to worry about such things. Most games go over 120fps at 4k. Set a frame cap limit in Nvidia control panel and you're 300w in most games. Then when you need extra power for the games where it can scale up.
Click to expand...
Yes but that's at 300W, I need to go down another 100W.
 
deama said:
Yes but that's at 300W, I need to go down another 100W.
Click to expand...

The 4090 won't be the best card for that. I'm estimating the 4080 will offer likely near identical performance at 200W and the 4070 will also likely be reasonable at that level (and AMD).

You lose nearly a 1/4 of the performance default at 225W according to the youtubers. But substantially more trying to go lower than that.

www.youtube.com

The RTX 4090 Power Target makes No Sense - But the Performance is Mind-Blowing

Support me on Patreon: https://www.patreon.com/der8auer---------------------------------------------------------Save 10% on your iFixit purchase: DER8AUER10h...
www.youtube.com www.youtube.com
 
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Could be they are running from solar, or a generator. It's not impossible to imagine a situation with a strict power budget.

I agree that 4090 is a bad fit, you're having to set it right down to it's minimum voltage to have a chance of hitting 200w and even then it will probably exceed it in some scenarios, there's not going to be any way to hard cap it at 200w without incurring the stuttering you've seen in reviews because you are off the end of the power efficiency curve.
4080 by comparison will almost certainly just work, set the power target at 60% and you are done.
 
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