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260 gtx 55nm Voltmod help

Discussion in 'Overclocking & Cooling' started by Chainspike, Mar 20, 2010.

  1. Chainspike New Member

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    Hi,

    I own a pair of 260 gtx rev.1 55nm cards. They are growing older and i was looking into bumping up their performance a bit with a hard voltmod. I know the risk of voltmoding etc.. I've volt modded my 8800 gt's, so I'm not new to the soldering and stuff. I can do all the work the only problem is I'm not sure what needs to be removed or added in order to increase gpu voltage and also cancel out the ovp/ocp. Below is pictures of my pcb layout and the NCP 5388 data sheet. PLZ if could help me out NO ONE HAS a voltmod guide on 260 gtx 55nm rev.1 or 2.

    [​IMG]
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    This is the best pic could get of anything to a guide to volt mod it. If you could expand a little as to step by step instuctions would be great since the pic was taken from a german modding site.

    [​IMG]


    Theres a link to the NCP 5388 datasheet

    http://datasheetz.com/ONSEMI/NCP5388-D/NCP5388-D.html



    p.s. the resistance between pin 19 and ground is 12.5 k ohm
     
    Last edited: Mar 20, 2010
  2. angelkiller

    angelkiller

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    Alright, here's my guess. I'm by no means an expert and you probably want someone to verify what I say.

    I'm going to assume that the voltage controller you have is the one you linked the datasheet for.

    Anyway, the principle of volt modding is to lower the resistance on the 'feedback' pin of the voltage controller. This increases the voltage on the pin. The voltage chip is constantly monitoring and adjusting to get the right voltage. When the controller sees the higher voltage, it somehow (not quite sure here) interprets this as "the GPU voltage is too low" so it increases the voltage on the GPU. What you're basically doing is tricking the voltage controller into giving the GPU a higher voltage, by tricking the controller into thinking that the actual GPU voltage is lower than it really is.

    That third picture (blue pcb) has highlighted Pin 19, which on that controller (according to that datasheet) is the voltage feedback pin. The other red dots show where that pin is connected to, so any of those points work. So you want to lower the resistance on that pin. The general practice is to attach a large resistance from that pin to ground. A variable resistor anywhere from 20k to 50k may work. I would start with 50k and lower as necessary. You say what the resistance is now, but unfortunately I don't know what it 'should be'.

    Something you're still missing is a vGPU measuring point so you can monitor your progress. On one of my (Asus 4830) cards, I get a vGPU reading off a (filtering) capacitor to the left of the chokes. Poke around for the core voltage. After looking at your card, try connecting one of these to ground.

    Also I take it that you short those other pins to disable over current protection, which is OCP in the pic.

    And I'm sure someobody has a guide for voltmodding this card. I'll look around. Hope this helps.
     
    Last edited: Mar 20, 2010
  3. Chainspike New Member

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    Ty

    Ty for your response. I do have a measurement point for the mem and gpu. It's currently at 1.18v from my soft bios mod upgrade from the 1.12v.

    Trust me... There is no guide for 260 gtx 55nm what so ever. I found a guide for Rev.2 but it was very rough and rev.2 uses a different voltage controller. The only thing could find was a german site and they used a 210K ohm varibale resistor since my resistance was about the same as theirs. I even tried posting on there site in the hopes they speak english for more information. That didn't work out to well... Here's the link..
    http://babelfish.yahoo.com/translat...ad.php?t=5865&lp=de_en&.intl=us&fr=yfp-t-701\

    They provide some useful info but it is far from an actual guide on how to do it. The problem is they don't say clearly how they disabled the OVP. The OCP they just shorted out the two pins in the picture. The gpu voltage they connected a 250k variable resistor from pin 19 to ground. I believe the layout is similar to 285 gtx. This would mean that I have to remove a resistor (which one???) and replace it with a variable resistor (which size?). The 285 uses a 100k ohm variable resistor to disable OVP and a 100k ohm variable resistor to change gpu voltage.
     
  4. angelkiller

    angelkiller

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    Holy crap. I read that link and now I'm even more confused.

    I have never dealt with over-current protection nor over-voltage protection. So I really can't help you there. My only question is how do you know they get in the way?

    You said that you had to 'remove a resistor'. Are you talking about doing that to increase GPU voltage or to disable OVP? If I understand things correctly, the volt mod alone only requires you attaching a pot from pin 19 to ground.

    Another way to find info is to look for a mod that uses your same PCB. For example, I found a volt mod for an Asus 4850, but it worked on my Asus 4830 because they use the same PCB. I don't know exactly what model you have, but maybe MSI uses that same PCB in another model? Does the GTX 285 mod you were talking about have the same PCB/components?

    You also might want post at XS or OCN for this. They both have pretty good volt mod people there. (Sorry!! I still love you TPU!!)

    Edit: What is the voltage on those points I gave earlier?
     
    Last edited: Mar 20, 2010
  5. Chainspike New Member

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    Ok this is what I did. I bought a variable resistor and set it to 150k for about 1.26v-1.23v. I soldered a wire to pin 19 check it. Gave 12.5 ohm when connected to ground when reading it from the end.. Perfect!! I soldered two wires into c1069 for easy gpu voltage reading. Heres the weird part. It boots fine and runs good. Voltage is 1.06v at idle. When I go into a 3d app it simply reads 1.18v. This is the same voltage before the mod??? I checked the the resistor and it reads 150k ohm. Now I am really lost.... How can it just have zero impact? I'm going to double check my connections.
     
  6. angelkiller

    angelkiller

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    After you do the mod, shouldn't the resistance between pin 19 and ground drop? You've added some resistance in parallel, so the overall resistance should fall a little, no?

    After you do the mod, all you voltages will go up. So if you were getting 1.06 idle before, that should be higher also.
     
  7. Chainspike New Member

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    YES YES!! you are right. Ty. Now that you mention it.. it did drop from 12.5 to 11.2. I guess will have to lower the resistance. Also It did increase from a solid 1.18 to 1.186 hmm maybe just need to adjust more. Let me try 100k ohm resistor and get back to you. A good thing is that I haven't ran into OVP or OCP yet..
     
  8. Chainspike New Member

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    Ok, heres an update. I can get up to 1.23-4ish before the OVP kicks in. I have no clue how to disable the OVP and cant seem to find any info on it. I was able to get a nice 800/1600 clock at 1.24v. I also disabled the OCP using the mod shown.
     
  9. mswezey New Member

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    Hey I read what you did
    Thats awesome!

    Can you do a mini write up with pics? I would like to do the same as you did as I have the same card as you do.
     

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