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Discussion Starter #1 (Edited)
I posted this in the RTX 3090 owners club thread and I'm posting this here for more visibility to anyone who might stumble across this:

Edit: Added note about 6th shunt resistor & updated images

Tonight I successfully shunt modded my RTX 3090 FE. It's a pretty straightforward process, just like Turing.
The method I used was replacing the R005/5mOhm resistors with 3mOhm Panasonic current sense resistors. I was afraid stacking 5mOhm resistors on top of the originals might cause clearance issues with the cooler. Besides, I'd always recommend replacing the resistors over stacking them for good measure.

There are 5 (five) 6 (six) resistors in total you need to replace. 3 of them are on the back of the card, and 3 on the front. (The 6th is not circled, but is on the front of the card near the springy push-pins for the fans - if the card compares values from each resistor, it's definitely a good idea to replace the 6th as well.

Though I may be wrong on that, one might not have to replace all 5 or 6 resistors, I only did it because I wanted to be absolutely sure the shunt mod would be effective and I was rushing. So if anyone has the time to test replacing these one by one please let me know your findings and I can update this.
For the time being though until some evidence comes out otherwise, I'd just replace all of them.

Resistor power limit info:

Replace or StackOriginal ResistorNew (or stacked) ResistorMax Power Draw
Original/Vanilla5 mOhmN/A366 W
Stacked5 mOhm3 mOhm976 W*
Stacked3 mOhm3 mOhm732 W*
Stacked5 mOhm8 mOhm594 W*
Replaced5 mOhm3 mOhm610 W*
*Numbers coming from 'ShuntMod Calculator' by bmgjet


They are easy to spot as they are the only R005 resistors on the board. It's pretty easy to remove them using a heat gun and a pair of tweezers (be VERY careful not to disturb other components!!)

3090_shunt_resistors_back.png
3090_shunt_resistors_front.png


^ There is also a 6th shunt resistor next to push pins on the right side of the front on the card - I forgot to circle this one before, I've updated the images. I have not noted any difference with this shunt resistor replaced, though you might want to replace this one as well. I've also marked the ground & +12V on the 12-pin connector in case you want to trace these yourself. The resistor closest to the PCIe socket on the rear should be measured through the PCIe power pins.

Once they are removed, use some solder paste and carefully place your new resistors on and heat them up w/ the heat gun until the solder melts, ONE AT A TIME! And again being very careful not to disturb other SMDs. This way you don't need to bother with using a soldering iron, and you can get this done pretty easily if you have the worst soldering skills like me.

I am still waiting on my water block to arrive so I'm not able to really push the card in long tests yet, but in short bursts I can get it up to around 2150Mhz before the temp spikes up.

Prior to this mod on air I was only able to get around 1930mhz stable in demanding 3D applications or 2010mhz in less demanding applications.
Post mod I am now able to get 2040mhz stable on air (with a crap-load of airflow) and I suspect I should be able to get at least 2100mhz stable on water once my block arrives.
I used these same resistors when shunt modding my Titan RTX cards and had great results with 3mOhms.

I'm attaching images of the front & back of the card with the resistors circled that need to be changed from 5mOhm to 3mOhm

This should work on the RTX 3080 FE as well by replacing all of the 5mOhm resistors, I've attached images of the 3080 PCB with all the resistors circled for a working shunt mod on that card as well. I've written 3080 in big red letters on those images, so be careful not to get them confused when trying to locate the resistors on your specific model.

The resistors I used can be bought from DigiKey here

Note: Do this at your OWN risk! These are $1,500 GPUs, and shunt modding will absolutely void your warranty. They can pretty easily tell during RMA if you botched a shunt mod and will not honor your warranty. If you do this, make sure to save the original resistors in an anti-static bag in the event you sell the card in the future.
 

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Nice Job ;)(y) on the card mod, and thanks for posting this here to as well. This way it reaches out to far more people in case they happen to have missed out on the 3090 owners club. I'm currently waiting upon a 3090 Strix, and was hoping to get a vbios mod of some sort down the road, I guess time will tell once that becomes available on the forums. However thanks again and good luck (y)
 

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Discussion Starter #4
Any idea how much power you were drawing from the card before and after? Just genuinely curious how much more power the 12 pin us pulling.
Around 350 to 360W before the mod, around 370 - 440W (OC dependent) after if my kill-a-watt is right. I have a dedicated PSU for my GPUs. With a stronger OC on water and pushing the power limit higher I may be able to get a bit more, but I am now hitting the voltage limit of the GPU itself but I've kept the OC relatively tame for the time being as even with chilled air a moderate OC can quickly overcome the cooling solution. So with this shunt mod, I've removed the power limit but I'm now stuck at the GPUs volt limit.
 

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You sir are awesome. I have this card and have been wondering what to do. Now my only delimmea is to wait and get a StriX or a Kingpin, or just go all out with the FE. I also have a waterblock on the way the bykski.
 

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Discussion Starter #7
Awesome thanks!
Would you be willing to run furmark to see what the max wattage used by the card after the mid would be? Trying to find what may be the weetspot for the resistors to try and pull 500-550 watts as I may go this route.

Thanks for adventuring into the unknown for us!
I will absolutely do this once I have my water block. Right now on air I can't get things significantly stable enough for a true test of the max power draw. Though from my really horrible math the theoretical max draw should be somewhere close to 600W (in reality it'd probably be around 550 to 580W)
I can guarantee though that using 3mOhm resistors you can easily set your power target and have it draw 500 to 550W based on the math.
You'd just need to play with the power limit in Afterburner post mod until you found that sweet spot using a kill-a-watt or something.
 

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Thanks! I'll be looking at doing this once my block arrives.

When running the stock fan curve I'm getting a max fan speed of about 2000rpm at 400W during a Port Royal stress test. My GPU temp is actually lower at max power limit than stock. Probably due to memory temp. Is this behavior the same for your FE's? I am beginning to wonder if the thermal pads aren't installed properly on my card.
 

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Discussion Starter #9
Thanks! I'll be looking at doing this once my block arrives.

When running the stock fan curve I'm getting a max fan speed of about 2000rpm at 400W during a Port Royal stress test. My GPU temp is actually lower at max power limit than stock. Probably due to memory temp. Is this behavior the same for your FE's? I am beginning to wonder if the thermal pads aren't installed properly on my card.
Nah mine was doing the same thing, as soon as I shunt modded it that changed immediately and the card began going from stable temps on air around 68 to 70 C to around 85 to 90 C when maxing the power limit. They definitely put some heavy restrictions on power draw this gen, hence all the resistors, and I agree that it's probably something to do with the memory heat. I'm currently trying to think up a solution to water cool the memory on the back side of the card better than the bykski backplate. I'm kinda worried about the longevity of the memory on the back of the card when overclocking it now
 

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Nah mine was doing the same thing, as soon as I shunt modded it that changed immediately and the card began going from stable temps on air around 68 to 70 C to around 85 to 90 C when maxing the power limit. They definitely put some heavy restrictions on power draw this gen, hence all the resistors, and I agree that it's probably something to do with the memory heat. I'm currently trying to think up a solution to water cool the memory on the back side of the card better than the bykski backplate. I'm kinda worried about the longevity of the memory on the back of the card when overclocking it now
I have ordered some Fujipoly thermal pads to replace the stock ones. These should have much better thermal conductivity. I'll retest after the swap to compare.

Watercooling the card should decrease the temp on the entire board and help thermals even on the rear memory modules. I'm still waiting for the EK one which they have teased. I have a feeling this might have some extra cooling on the rear.
 

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Discussion Starter #11
I have ordered some Fujipoly thermal pads to replace the stock ones. These should have much better thermal conductivity. I'll retest after the swap to compare.

Watercooling the card should decrease the temp on the entire board and help thermals even on the rear memory modules. I'm still waiting for the EK one which they have teased. I have a feeling this might have some extra cooling on the rear.
It absolutely needs cooling on the rear of the card. The memory modules get insanely hot. I'm also waiting for the EK block. They teased it a while ago and still haven't said anything else about it, so hopefully they are working on some sort of solution for the back of the card. Honestly, I'd LOVE to see someone release a dual block for front and back. As of right now I'm thinking of doing what someone in the 3080 Owners Club thread did and buy one of those Bykski ram blocks and somehow mounting it on the backplate to help remove some of the immense heat.
 

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Nah mine was doing the same thing, as soon as I shunt modded it that changed immediately and the card began going from stable temps on air around 68 to 70 C to around 85 to 90 C when maxing the power limit. They definitely put some heavy restrictions on power draw this gen, hence all the resistors, and I agree that it's probably something to do with the memory heat. I'm currently trying to think up a solution to water cool the memory on the back side of the card better than the bykski backplate. I'm kinda worried about the longevity of the memory on the back of the card when overclocking it now
Everything on the back of the card is going to be high-temperature tolerant and doesn't need truly active cooling. If I were just "getting it done" I'd slap a 10mm thick finned heatsink on it and call it good. Even sitting 70C it'll be fine forever.

Fun fact, years ago I CAD'd up a GPU backplate for this purpose. Absurd expense though to get it prototyped though so never had it actually made. Somewhere in the $150 range and then EK makes a backplate available for $20.

2461300


I'll maybe look into waterjetting a bracket to hold down the Bykski ram block to a backplate, but the problem with that is every backplate uses different mounting points. Some use only screws on the edges, some use ones around the core, etc.
 

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Discussion Starter #14
can you share what heatgun you used?

i'm scared of using one because of the components in rnage of the shunts and would probably just stack 5ohm on them

maybe this one would work with the small nozzle? SEEKONE Heat Gun 1800W Heavy Duty Hot Air Gun Kit Variable Temperature Control with 2-Temp Settings 4 Nozzles 122℉~1202℉(50℃- 650℃)with Overload Protection for Crafts, Shrinking PVC, Stripping Paint - - Amazon.com
I used a similar one to that, but Black and Decker that I purchased at Lowes. That one would work fine. It's ok to heat up the surrounding components as long as you do not disturb them!!!!!!!!!!!!!!!!!
It takes an extremely steady hand. Just heat them up until the solder melts and using very pointy fine tweezers, lift (do not slide) the old resistors off the pads. Then throw down some solder paste, place the new resistor down, turn the heatgun on LOW mode (high heat but low speed) and melt the solder paste affixing the new resistor in place. If your nervous about it I wouldn't do it, as being nervous can cause shaky hands. I had to have someone else pull the last 2 resistors for me because my hands were shaking so damn bad lol
 
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What size fujipoly are needed? Any recommended thermal compound these days, liquid metal? Ordered resistors for shunt mod. I can't break 13500 on Port Royal due to power limit throttling right now. =/
 

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Discussion Starter #16
What size fujipoly are needed? Any recommended thermal compound these days, liquid metal? Ordered resistors for shunt mod. I can't break 13500 on Port Royal due to power limit throttling right now. =/
I'm not certain on thermal pad sizes yet, still waiting on my water block which won't arrive for another week yet. For thermal compound I highly recommend something like Thermal Grizzly Kryonaut or Arctic Silver. Just use a high quality paste and you'll be fine. I wasn't able to get past 13700 on Port Royal either due to the power constraints, and now that I'm shunt modded on air I can't get past 13900 due to heat constraints :p I haven't yet tried running Port Royal with the air conditioner hooked up to the PC, but even with that I doubt I'd make it past 14000 as this card gets f'ing hot. Definitely need to water cool after shunt modding or use LN2, no exceptions. I used to have a shunt modded Gigabyte Windforce GTX 1080 that was shunt modded back in the day which actually did just fine on air, but the 3000 series just get ridiculously hot.
 

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I'm not certain on thermal pad sizes yet, still waiting on my water block which won't arrive for another week yet. For thermal compound I highly recommend something like Thermal Grizzly Kryonaut or Arctic Silver. Just use a high quality paste and you'll be fine. I wasn't able to get past 13700 on Port Royal either due to the power constraints, and now that I'm shunt modded on air I can't get past 13900 due to heat constraints :p I haven't yet tried running Port Royal with the air conditioner hooked up to the PC, but even with that I doubt I'd make it past 14000 as this card gets f'ing hot. Definitely need to water cool after shunt modding or use LN2, no exceptions. I used to have a shunt modded Gigabyte Windforce GTX 1080 that was shunt modded back in the day which actually did just fine on air, but the 3000 series just get ridiculously hot.
What I don't understand is how some people have been getting above 14,000 with stock cards that don't have a power limit removed.

With a voltage curve there should be no reason why I can't continue with my existing temps using the clocks I have been using right? First time doing a shunt mod but familiar with voltage dividers.
 

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Discussion Starter #18
What I don't understand is how some people have been getting above 14,000 with stock cards that don't have a power limit removed.

With a voltage curve there should be no reason why I can't continue with my existing temps using the clocks I have been using right? First time doing a shunt mod but familiar with voltage dividers.
With a decent curve yeah. Once you do the mod, just play around with the curve until you find that sweet spot of perf and temps.

Also I have a suspicion on that. I think the silicon lottery for the 3000 series just has a larger gap. Couple that with better cooling solutions and different stock OCs on other cards and that's probably why you are seeing others break 14k or more.
 

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With a decent curve yeah. Once you do the mod, just play around with the curve until you find that sweet spot of perf and temps.

Also I have a suspicion on that. I think the silicon lottery for the 3000 series just has a larger gap. Couple that with better cooling solutions and different stock OCs on other cards and that's probably why you are seeing others break 14k or more.
I saw someone in the owner's thread mention using an 8mOhm resistor. What would the benefit be of that over a 3mOhm? From my (limited) understanding of how voltage dividers work for reading current draw the lower the resistance the less the card is going to think you are pulling. Would this just be to set a hard limit of 600W, for example?
 

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I'm not certain on thermal pad sizes yet, still waiting on my water block which won't arrive for another week yet. For thermal compound I highly recommend something like Thermal Grizzly Kryonaut or Arctic Silver. Just use a high quality paste and you'll be fine. I wasn't able to get past 13700 on Port Royal either due to the power constraints, and now that I'm shunt modded on air I can't get past 13900 due to heat constraints :p I haven't yet tried running Port Royal with the air conditioner hooked up to the PC, but even with that I doubt I'd make it past 14000 as this card gets f'ing hot. Definitely need to water cool after shunt modding or use LN2, no exceptions. I used to have a shunt modded Gigabyte Windforce GTX 1080 that was shunt modded back in the day which actually did just fine on air, but the 3000 series just get ridiculously hot.
Good to know. I've seen a few reviews saying the stock FE air cooler works almost as well as a custom water loop. Sounds like this is not entirely true. How many watts were you pulling on the Port Royal bench that scored 13900. I was thinking about performing the shunt mod and tuning for about a 450W draw, which is about all my PSU can handle.
 
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