# Radeon HD 4870 Voltmods



## W1zzard (Jul 8, 2008)

Show article


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## erocker (Jul 8, 2008)

Wow, that's a tiny place to soldier for the VDDC!  I better not have any caffiene that day!  Thanks so much W1zzard!


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## intel igent (Jul 8, 2008)

holy shizzlet! Volt mod's already!


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## Mmatao (Jul 10, 2008)

test of shappire 4879 gpu vmod, fan to 42% stock cooler.
room to 27º C

test passing atitool
without vmod 76º C 1.26v max gpu 770mhz
with vmod resistance 100 oms 79º C 1.28v max gpu 820mhz
with vmod resistance 50 oms 82º C 1,295v max gpu 825 mhz

the best configuration is 100 oms to stock cooler.

I do not understand mvddc and mvddq,  as is the one that there is to fit?


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## W1zzard (Jul 11, 2008)

erocker said:


> Wow, that's a tiny place to soldier for the VDDC!  I better not have any caffiene that day!  Thanks so much W1zzard!



unfortunately there is no better place to solder. on the other side there may be some spots but with the cooler on top its kinda difficult to put wires there.


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## mat9v (Jul 14, 2008)

Could somebody per chance check if AMD GPU Tool really changes voltages? I don't have a multimeter and have no way to check... please somebody?


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## W1zzard (Jul 14, 2008)

vddc reading spot fixed, the picture in the article now points to the correct location


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## chron (Jul 15, 2008)

I thought these cards had "dynamic voltage control" so you wouldn't have to do all this?


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## W1zzard (Jul 15, 2008)

yes you can change up like 0.1v in software and down about 0.3v .. in 4 steps. but at this time there is no software to control voltages, other than modding the bios


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## Haste (Jul 16, 2008)

W1zzard said:


> yes you can change up like 0.1v in software and down about 0.3v .. in 4 steps.



Hi. What do you mean with the "in 4 steps" ? I've modded the 4870 BIOS using RBE 1.11 but it doesn't seem to have any effect on voltages. I tried increasing it from 1.263 to 1.276 and 1.302 but without success. The vcore was not changed. So is there another way to up the GPU voltage by 0.1v? Thanks.


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## W1zzard (Jul 16, 2008)

the card can only select one voltage out of four. so there is something like 1.0, 1.1, 1.2 and 1.3. the card has to pick one, ther is nothing like 1.15 possible in this example. 
i dont know the actual voltages that are implemented.

did you change the right profile? i think a 0.1 increase should be possible


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## Haste (Jul 16, 2008)

Yes, I think so. In the RBE it has high profiles at 3 and 9. 4 to 6 are UVD profiles. I've changed the 3 and 9, both to the same voltage I mentioned before. Now I have it at 1.363 (exactly 0.1v above normal) but no success again. Even people from XS forum didn't have any luck with BIOS voltage mod so i feel a bit skeptical about it. I would appreciate any help with the mod. I'm willing to try almost anything... have my old PCI card ready if necessary


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## The Haunted (Jul 19, 2008)

I didn't find a 50 ohm pot locally. Does a 100 ohm 15 turn one would be precise enough to reach high voltages (1.5-1.6).
 Or a 20 Ohm one would be better suited ( i have both ).


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## Haste (Jul 19, 2008)

I'd recommend fixed 20ohm resistor and I really hope that you have water cooling at least. 20ohm ~ 1.5-1.6v. And be careful, that vddc solder point is really tiny.


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## The Haunted (Jul 19, 2008)

With a tiny spot like this could i put some hot glue on it after the wire is soldered to ensure it doesnt break?


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## Wshlist (Jul 24, 2008)

In a what I consider related story: I stumbled upon a forum with a post by a guy who made some images with a thermal camera of his 4870, and you can see some interesting result from the voltage converter area.
Translated link:
http://translate.google.com/transla...hread.php?t=510938&hl=en&ie=UTF8&sl=d e&tl=en

Note how he writes the GPU-Z values reported above the pictures, so keep in mind that those sensors on the board only tell so much.


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## rflair (Aug 15, 2008)

From my testing doing the GPU Vmod with fixed resistors,

33 Ohm=1.35v idle 1.37v load

27 Ohm=1.37v idle 1.39v load

22 Ohm=1.385v idle 1.405v load


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## rflair (Aug 16, 2008)

Anyone know how much resistance is needed to raise the memory voltage to 1.6v ?


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## philbrown23 (Sep 8, 2008)

anyone have a picture of the actual mod yet? I wanna see some working mods before I decide to take the dive.


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## 4870's@over (Sep 12, 2008)

Who knows if using 4600Mhz in the memory card without artifacts could kill?


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## nasone32 (Sep 24, 2008)

hi, I would like to show you my card. its pcb is slightly different from the one in the vmod guide, the vgpu soldering point is covered and there are a few more transistors around. it's a club3D 4870 oc'ed edition.
I would like to know if the soldering points are the same (probably yes).
sorry for my bad english, I'm Italian


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## tress972 (Oct 15, 2008)

I'm looking around & I heard about some pencil VDDC mod on 4870...











Did somebody try them ?


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## nasone32 (Oct 18, 2008)

sorry but where is the pencil-point located in your pictures? can't see anything...


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## 4870's@over (Nov 28, 2008)

Guys, I have a PowerColor 4870, but with more than 825 in the Core she presents a strange behavior, I have BSOD.

How to resolve?

BIOS OCX 1.276v


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## ShadyAchmed (Dec 15, 2008)

RMA - sounds like U got a bad card.

I have the same card, I get 850/1100 stable - everything maxed out, w/ a Scythe Musashi cooler.  http://www.scythe-usa.com/product/vga/002/scvms1000_detail.html   Runs great - no problems at all.  

I actually have two of these cards, same story on both.  Crossfire doesn't scale well at all on my system.  Card was unstable in crossfire, OC'd  or stock.  Running a single card - excellent performance!  Maybe my next rig (and later drivers) will better support them in crossfire.

Running it w/ a QX9650 OC'd to 4.2Ghz.


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## Cherub (Dec 31, 2008)

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


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## Cherub (Jan 27, 2009)

Cherub said:


> How about an update for non-reference boards, like this one from Sapphire here.



I'll take it the answer is no...


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## KBD (Feb 3, 2009)

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.


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## albinowino (Mar 9, 2009)

Cherub said:


> How about an update for non-reference boards, like this one from Sapphire here.


Belatedly, this might help 



KBD said:


> 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.


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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## KBD (Mar 9, 2009)

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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## nasone32 (Mar 9, 2009)

i've succesfully done the vmod to my non-reference 4870 512mb, an OC edition by club3D.
as you can see here 


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 ).

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.


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## runkner (Jan 20, 2011)

*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


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## nasone32 (Jan 20, 2011)

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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