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General GPU Voltmod and External VRM Information

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post #21 of 30 (permalink) Old 05-24-2018, 10:13 AM
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Quote: Originally Posted by mllrkllr88 View Post
Hey

Not sure I completely understand the question, you should reference a specific card so we can look deeper. I have seen a few very gold cards, like 6600GT for instance, that use linear regulators for things like memory. So on a few very rare old cards its not possible, however, most cards I have come across are using a buck converter style power management which means you should have the ability to adjust voltage in real time.
I found a PCB breakdown from buildzoid for a R9 290X, the card actually uses one single voltage controller and has two voltage sense pins, one for vcore and one for vmem. I didn't find any information about voltmodding both vcore and vmem if both voltages are controlled by the same controller, and wondered how people do it. It seems such x+x voltage controllers actually have two sense lines so its actually really easy.

Another question I have is how do people find the the FB pins without having the datasheet for a voltage controller ? How do you do it if you dont have access to the datasheet ?
I just ordered some potentiometers,disable switches and voltage displays to do my first practice voltage mod on an old 8800GTS, there is a datasheet for the memory voltage controller so I know where the FB pin is but there is no public datasheet for the core voltage controller and I only know where the FB pin is because some people on the internet found it, but how?

Because I want to do some DryIce overclocking on cards like my 980Ti, not knowing how to find the FB circuit would be a problem. My 980Ti uses an uP1984A and there is literally no information about it anywhere. There is a uP1983 with the datasheet available to the public but the pinouts are completely different (checked with a multimeter) so I would need to find the FB pin some other way.

Thx for sharing all your knowledge about voltmodding with this thread
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post #22 of 30 (permalink) Old 05-24-2018, 02:28 PM - Thread Starter
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There are several cards that use a single controller, one that comes to mind is the HD7970. It uses the CHL8228 which does indeed have two independent controllers built into one IC. You can see in the datasheet HERE that pin 6 is VSEN for core and pin 38 VSEN_L2 for MEM/PLL. Those are each independently controllable feedback resistances for increasing or decreasing the different voltage levels.

As for finding the feedback or sense lines without a datasheet that can be tricky. I have done is many times now but it takes diligence and some reverse engineering. I look at several datasheets by the company which are available and look for patterns in the layout. Then I make some educated guesses based on my findings and so far I have not killed anything. For beginners, if you cannot find the datasheet, or you cannot find/dont want to use internet mods...then its best to just not even go there.

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post #23 of 30 (permalink) Old 05-24-2018, 02:45 PM
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Quote: Originally Posted by mllrkllr88 View Post
There are several cards that use a single controller, one that comes to mind is the HD7970. It uses the CHL8228 which does indeed have two independent controllers built into one IC. You can see in the datasheet HERE that pin 6 is VSEN for core and pin 38 VSEN_L2 for MEM/PLL. Those are each independently controllable feedback resistances for increasing or decreasing the different voltage levels.

As for finding the feedback or sense lines without a datasheet that can be tricky. I have done is many times now but it takes diligence and some reverse engineering. I look at several datasheets by the company which are available and look for patterns in the layout. Then I make some educated guesses based on my findings and so far I have not killed anything. For beginners, if you cannot find the datasheet, or you cannot find/dont want to use internet mods...then its best to just not even go there.
I will just link you to a part of one of buildzoids videos where he explains how he found the FB circuits (minute 4:40) on cards like his Vega 64 Vega 56 and pretty much every card he has ,without having a datasheet. Have you heard of this method ? Sounds better than guessing to me :/

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post #24 of 30 (permalink) Old 05-24-2018, 05:23 PM - Thread Starter
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His "method" is not a method which you could apply to a broad range of GPUs. He is literally doing the exact same thing I described to you above. He is simply looking for the patterns in the layout based on designs which have datasheets for.

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Last edited by mllrkllr88; 07-23-2018 at 10:07 AM.
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post #25 of 30 (permalink) Old 05-25-2018, 02:02 PM
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Did you cut that external VRM off another card and are you using these two Voltage Regulators to supply the 3.3V and 5V ? And why did you short 3pins together on the 8pins ?
For some reason I cant upload the picture here so I uploaded it on Imgur.

https://imgur.com/S5bB96E
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post #26 of 30 (permalink) Old 08-30-2018, 06:34 AM
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Hey mllr, could you add the solder and flux you use for the copper plate epower mounts?


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post #27 of 30 (permalink) Old 08-30-2018, 09:55 AM - Thread Starter
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Quote: Originally Posted by bigblock990 View Post
Hey mllr, could you add the solder and flux you use for the copper plate epower mounts?
If you want to skip all the junk flux out there (at work I have tried 20+ different ones) and go straight to the best on earth then its Kester brand "Rework" style flux. You can get liquid style pens like I linked up in OP, or for heavy EPower plate modding you would probably prefer a thicker paste. I typically don't use any added flux, but it certainly makes your job easier.


There are many "rework flux" options but I have used both of these and I would highly recommend either:
RF771: https://www.kester.com/products/prod...71-rework-flux
RF741: https://www.kester.com/products/prod...41-rework-flux


You can find them on Amazon: https://www.amazon.com/Kester-RF741-...ct_top?ie=UTF8


FYI: These are "no clean" which means they are not electrically conductive so you can leave it on your PCB and it wont cause problems. However, I would always recommend cleaning your work after you are done with a small bristle brush (toothbrush works well) and alcohol.

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GPU
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RAM
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Power Supply
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Cooling
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Cooling
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post #28 of 30 (permalink) Old 10-08-2018, 01:09 AM
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Thanks, it helps me alot.
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post #29 of 30 (permalink) Old 10-10-2018, 02:21 PM
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Today my K|NGP|N TEK-9 Fat arrived to do my first ever DryIce session with a 980Ti Classified (so I dont have to worry about hardmods the first time).
I plan to use a lot of paper towel and kneadable art eraser for insulating the GPU and the area around the PCIE slot.
However I didnt buy any armaflex or somehting else for the LN2 pot. Do you guys have any tipps ?
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post #30 of 30 (permalink) Old 02-06-2019, 12:59 AM
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Necro'ing the thread; it's still very relevant


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