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    How do I pencil mod my 4870m? (datasheet for VR provided)

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by moral hazard, May 5, 2012.

  1. moral hazard

    moral hazard Notebook Nobel Laureate

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    I would like to increase the voltage to my 4870m, I have found the voltage regulator on the card, datasheet is here:
    http://ceemic.pri.ee/hardware/datasheets/ADP3208.pdf

    I have tried to shade in the resistor coming from the FB pin, but that didn't work (notebook didn't show anything on the screen so I had to remove the shading).

    Any advice?

    I don't care if I burn the card, I just want to get it past 700mhz stable with the latest drivers.
     
    moral hazard, May 5, 2012
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  2. Greg

    Greg Notebook Nobel Laureate

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    Not that I am recommending this or anything, but it looks like you'd have to cut VID0-VID6 and hardware them to VCC or 0V in order to set a specific voltage. Do not just short the pins together and hope for the best. Modifying anything related to the FB pin is going to negate the chip's ability to monitor the core voltage properly and could quickly damage the card. Obviously not a recommended procedure.
     
    Greg, May 5, 2012
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  3. moral hazard

    moral hazard Notebook Nobel Laureate

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    I thought about vid0-vid6 but that would take too long to solder (I dont have my tiny soldering tip), I want a quick and dirty job, a lot of people on desktop forums do the FB pencil mod with success, I don't see why it's not working for me, maybe I'm looking at the wrong pin, should I be looking at the FBRTN pin?
     
    moral hazard, May 5, 2012
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  4. Greg

    Greg Notebook Nobel Laureate

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    That pin is grounded, for good reason. Without modifying VID0-VID6 I'm not sure how you could mess with the feedback pin without ... well ... I'm not used to finding ways to violate specifications :D. My job is to follow specs, not trash them.
     
    Greg, May 5, 2012
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  5. moral hazard

    moral hazard Notebook Nobel Laureate

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    Ok, I will take another look at the board and see if I can do it your way ;)
    Flash the vbios to give the card 1.15V. Then connect vid4 to GND and hopefully get 1.35V (but then I will probably have to deal with over current protection and maybe the black screen that could result from that).
     
    moral hazard, May 5, 2012
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  6. Meaker@Sager

    Meaker@Sager Company Representative

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    You find the specs and then see how you can.... bend them.... :)

    Usually with me I find the resistor leading between FB and ground and shade along it, 10% difference in that resistance should lead to a 10% voltage rise.
     
    Meaker@Sager, May 5, 2012
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  7. moral hazard

    moral hazard Notebook Nobel Laureate

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    Thanks for that info Meaker.

    I found out why my first mod didn't work, the resistor I found originally was the wrong one (I was going by eye). But right now I can't find the actual resistor. Will look again later.

    I also connected vid4 to GND, but the voltage didn't change, I have to recheck my soldering...

    But I'll do that later, it's getting late.
     
    moral hazard, May 5, 2012
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