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Discussion Starter #1 (Edited)
Hi!

This is a guide on how to raise the target power limit of your GTX 1080 with a resistor mod. In my case, I used an EVGA GTX 1080 FE. Your card layout may differ from mine.
I am new to forums. Actually, this is one of my first informative posts. Feedback always welcome!

After doing some research about modding the shunt resistor on GTX video cards to raise power limits, I decided to do skip the liquid metal part because the composition of this metal could damage the resistor/tin and there is also a chance that the liquid metal could drip off the shunt and short other components. But beware that this is basically a permanent mod and can hardly be reversed. Also, some soldering and electrical skills needed!



Figure 1

What I did is soldering another resistor parallelly on top of the shunt resistor. The reason for soldering a resistor parallelly instead of replacing is because we are working with a very low resistance (1mOhm = 0,001Ohm), and putting your own calculated resistor with too much soldering tin will create an even bigger resistance where you can't know the exact resistance. Here you can see why:



Figure 2 & 3

The two bigger pads are where the current is mostly running trough and two tiny pads that are connected to the power measurement circuit. It's important to keep the resistor as close as possible to the solder pads for a more accurate measure.
I hear you thinking: but you are also raising the resistance if your soldering a resistor on top of it, isn't that the same? Not exactly, because if your value is not correct you can carefully solder it off and replace it with another value (I recommend to calculate it right at once). in brief, It's definitely an important aspect to think of if you are working with low resistance's.

As you can see in figure 1 I soldered a 6mOhm 1% resistor on top of the existing 2mOhm resistor, raising the card's power limit by 33%. I will explain how I calculated that.

I used the common formula for calculating parallel resistance :



Figure 4

In my case, I wanted to raise a maximum of 33% of the power limit.

That's going to be: 2mOhm / 100% * 25% = 0.5mOhm subtracting that from 2mOhm = an Rtot of atleast 1,5mOhm.
Subtracting 25% from the resistor increases the power limit by 33%:

2 mOhm / 1,5 mOhm * 100% = 133%

R1 = 2mOhm
Rtot = 1,5mOhm
We want to know R2, so the formula becomes:

= 6mOhm

Figure 5

After that, I assembled the card back together and tested it with Furmark.

Before the mod:



Figure 6

After the mod:



Figure 7

As you can see I gained a fair amount of core clock, and also the VDDC has more room to increase. I actually did need to lower the core overclock because it was running too fast and began to crash.
The tests were running quite short which is why the card was not running hot.
But I'm not sensing any extreme temperatures on the longer runs (30 mins on 100% fan speed), but this could be that I used liquid metal on the GPU die:



Figure 8 & 9

Now, you can extend it further than 33% but be aware that your card can run very hot or even blow up. So if you are planning to do this, calculate the resistance well, use a more extreme cooling solution (like custom water cooling) and keep a good eye on the temps so that the risks are minimalized.
After all, it's a limit to protect the card from breaking. Do it at your own risk.

Thank you for your time, I hope it was helpful. I will start shortly on my first hardline water cooling build which I will post pictures of too.



Graxx



P.S. Sorry if my English was bad, I'm Dutch :), also I had to use the word ''ohm'' because if I use the symbol, it gives an error while posting the threat.



My sources:

Google is your best friend

der8auer's video: https://www.youtube.com/watch?time_continue=3&v=v1Qi8fxIi_Y
 

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Hey dude, I know I'm late to this, but this is one of the best posts detailing a proper, reasonable shunt mod that I could find on the internet.

I'm planning to do this mod myself, so hopefully you or anyone reading this can help me to understand the maths of it better. What I'm thinking is this—doesn't this mod increase the power limit by 33%? -25% resistance on 2 mohm = 1.5 mohm, correct. But, 2 / 1.5 mohm = 1.33, so 217 W (EVGA GTX 1080 FE power limit) * 1.33 = 289 W, or 33% increase over the BIOS limit. Am I right or am I wrong?
 

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Discussion Starter #3
Hey dude, I know I'm late to this, but this is one of the best posts detailing a proper, reasonable shunt mod that I could find on the internet.

I'm planning to do this mod myself, so hopefully you or anyone reading this can help me to understand the maths of it better. What I'm thinking is this—doesn't this mod increase the power limit by 33%? -25% resistance on 2 mohm = 1.5 mohm, correct. But, 2 / 1.5 mohm = 1.33, so 217 W (EVGA GTX 1080 FE power limit) * 1.33 = 289 W, or 33% increase over the BIOS limit. Am I right or am I wrong?
Hello!

Thank you for your compliment, I really appreciate that.

About your calculation:

As you confirmed, 25% of 2mOhm is 1.5 mOhm. I indeed made a mistake to relate the 25% change in resistance with the output power.
I had to think of that the power (W), is relative to current (I) or voltage (U) because the calculation is squared (²).
This is what I should've done:


Example fixed value:
U = 12V

Situation 1:
R = 2 mOhm
P = U² / R so, 12V² / 2 mOhm = 72000W

Situation 2
R = 1,5 mOhm
P = U² / R so, 12V² / 1.5 mOhm = 96000W

Difference 24000W

100 * 24000 / 72000W = 33% increase.

Thank you so much for the heads up, I'm going to change it to 33%.


P.S. Maybe my calculation here is obsolete because you probably understand it quite correct, but yeah why not :)
 

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[...]

Thank you so much for the heads up, I'm going to change it to 33%.

Excellent, I'm glad I could help! I wanted to be sure because my card's power limit is already quite high and according to my tests I only need a small power increase for my needs (10-15%) and I don't want to kill my card.
 

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Hey dude, I know I'm late to this, but this is one of the best posts detailing a proper, reasonable shunt mod that I could find on the internet.

I'm planning to do this mod myself, so hopefully you or anyone reading this can help me to understand the maths of it better. What I'm thinking is this—doesn't this mod increase the power limit by 33%? -25% resistance on 2 mohm = 1.5 mohm, correct. But, 2 / 1.5 mohm = 1.33, so 217 W (EVGA GTX 1080 FE power limit) * 1.33 = 289 W, or 33% increase over the BIOS limit. Am I right or am I wrong?
Oh? You don't like the Roman method with a little dead headphone wire and eraser or hot glue? :lachen:
 

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Discussion Starter #7 (Edited)
Excellent, I'm glad I could help! I wanted to be sure because my card's power limit is already quite high and according to my tests I only need a small power increase for my needs (10-15%) and I don't want to kill my card.
Yeah true, 33% is quite high. However, it works just fine since 2018 now in my custom water-cooled PC. A good cooling solution is quite important for these mods:)

https://imgur.com/NFTBBRv
 

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Yeah true, 33% is quite high. However, it works just fine since 2018 now in my custom water-cooled PC. A good cooling solution is quite important for these mods:)

https://imgur.com/NFTBBRv

No doubt, although in my case I'm trying to get rid of peak power consumption limits rather than making it work at a higher power limit all the time. For that the standard air cooling should be sufficient.

Nice rig, btw.
 

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It's easy enough for me, so it's easy! :lachen:
Basically you're building a bridge over the resistor where power can get through without being monitored.
Find shunt..
Cut pieces of wire to fit shunt. ( I used 3-5 pieces of cut up copper dead headphone wire )
Lay on top of shunt....
And you can either hot glue or press eraser over it to hold it in place.
I used eraser bcuz what else ya gonna do with some old used eraser with shop towel bits in it? :lachen:
Press it on there nice and tight and flat and call it good!
I ran it for more than 2 years like that.
Thanks 2 Mr. Roman. Many thanks!
 

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Excellent, I'm glad I could help! I wanted to be sure because my card's power limit is already quite high and according to my tests I only need a small power increase for my needs (10-15%) and I don't want to kill my card.
The number of strands of wire determine how much power doesn't get counted.
 
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