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Radeon HD 4870 Voltmods

Discussion in 'Articles' started by W1zzard, Jul 8, 2008.

  1. Cherub New Member

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    How about an update for non-reference boards, like this one from Sapphire here.
     
  2. Cherub New Member

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    I'll take it the answer is no...
     
  3. KBD New Member

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    Are there any more specific voltmoding guides that can tell me what exactly has to be done when using the soldering method? For example, what needs to be soldred to the card, what are those 50 ohm things in the pic, resistors? And what kind of wire needs to be soldered to them and card? This is the kind of stuff that needs to be discussed in greater detail for those that dont know.
     
  4. albinowino

    albinowino New Member

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    Belatedly, this might help :toast:

    I don't know of any straight-up walkthroughs, I'm sure they're out there, but if you do more poking around with Google you should find some info. Basically what we're doing is shunting (that is placing a variable resistor into the circuit) a VR to modify the resistance that the power regulation senses and tricks it into believing that it's not supplying quite enough voltage, in turn it compensates with more voltage which is the end product we're looking for with higher clocks :) I like to use really tiny stranded wire like 26 or 30 gauge. Be mindful of the VR's resistance because there is a large difference between 50ohm and 50Kohm. Except where noted, we usually have to set the VR to the highest resistance (nominally a bit short of its exact rating, ex. 50K might show 45K max) and tune the resistance down once in place to tweak the voltage up. Use of a DMM (digital multi meter, goes for $10 on up) is imperative. You can set the direction of the VR's knob to tweak to your preference by using a different lead. Figure this out before soldering because you can't isolate a reading after soldering. It goes without saying that one false move could mess up your hardware so take every precaution. With practice it becomes very easy. Just get a 15w iron with the sharpest tip you can find (don't try to sharpen, they are specially plated), preferably a grounded iron (the plug has the third prong). Keep it tinned and clean for which there are many guides available. Luck be with you.
     
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  5. KBD New Member

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    albinowino, thats prolly the best explanation i've heard by far. I just think that TPU will benefit from a more detailed general soldering guide that can be applied to any card. This kinda of guide will be a great supplement to card-specific guides already available. I wasnt really asking about this only for my benefit, afterall my soldering skills are not good enough yet to do something like this (someday they will be hopefully), i think there are lots of folks out there who would like to try this but dont know the basics and lack of info (and may be confidence) discourages them from ever trying. So hopefully some knowledgeble member here will some day compile a nice guide for us beginners.
     
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  6. nasone32 New Member

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    i've succesfully done the vmod to my non-reference 4870 512mb, an OC edition by club3D.
    as you can see here [​IMG]
    unfortunately the vdimm & vddq is controlled by the same (single) vrm so overvolting memory makes absolutely no difference on clocks because the chip can't cope with the power requirements.
    feeding more voltage to mem causes only instability.
    the core has got 4 vrms instead of 3 of the reference, this makes the chip clocking quite nicely 920@1,37v, i'm on custom watercooling (the chip idles at 32°C and loads at 36°C :D).

    the card is not so much memory limited so i prefer having nice clocks on core instead of mem.

    i forgot to say that the soldering point on this card is the same of the reference one but the place is covered by paint so you have to scratch a little to do the job.
    here you can see the pwms of this card.

    hope this might help someone out there.
    [​IMG]
     
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  7. runkner New Member

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    4870oc'd

    what should the resistance between the vddc soldering point and gnd ?
    i made the mod but forgot the check it first.
    it was 3ohm when not connected to the trimpot
    and how many volts should i max have on the gpu and mem with stock cooling
     
  8. nasone32 New Member

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    on stock cooling i would probably leave it as it is or give just a very slight bump. if you have the same pcb as mine, leave mems at stock volts even if you have some proper cooling...

    however if you want, try it in small steps, just keep the temperature under control.

    for the resistance, use suggestions by w1zzard on the first page, start with the trimmer @ max resistance and decrease it slowly... unfortunately i sold my card so i can't make measurements, sorry.

    edit: if you read the first page, an user suggests 1,28v gpu on stock cooler
     
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