ATI 3850/3870 Voltmod thread

[ryanmartini]

You need a variable resistance that has 100k and lower, and then solder it onto the 2 points specified in the first post.

Maybe someone can explain better!

thanks. where can I find the variable resistor? Would radioshack have it?

Thanks!

Ryan

[LordEC911]

Ryan- supposedly they do.
There was talk in the 8800GT thread about it.

As for pics as to what it should look like, something like this but on a red PCB with a 100k pot and to the points marked in the first post of THIS thread. That picture is of a 8800GT Vmod.

[ghost101]

I have my 3850 stable @ 776/1125, when I hit 800 theres not enough voltage, the temps I get are 65C full load and 31C idle with the fan @ 70%

[IMG]ss[/IMG]

it seems like the 3850 has a lower GPU clock and mem voltage than the 3870.

Hi, which 3850 have you got? Also, does rivatuner overclocking work with CCC installed?

[Sage]

bring on the DDR3 volts!

[KainXS]

Hi, which 3850 have you got? Also, does rivatuner overclocking work with CCC installed?

I have the powercolor version

Im going to post some pictures of the back of the pcb to help you guys with vmods later

edit

3850



yes I know its huge

[Glow9]

So I see the pic with the green and purple dots what are you soldering to do this exactly? I'm confused

[largon]

Green = soldering point for outer leg of a VR
Blue = ground = solder middle leg of a VR
Purple = vGPU measuring point (red probe of a DMM to purple, black probe to ground)

[ryanmartini]

Christmas Project: Vmod 3870 with the DuOrb

[KainXS]

heres the 3850, imagehost keeps deleting it

http://www.yourfilehost.com/media.ph...27P1010374.JPG

[slugzkea]

Updated:

These mods need more testing, but initial results suggest they work fine.

Mods are carried out at your own risk. I will not take responsibility for any voltmods gone wrong. No-ones forcing you to mod your cards and invalidate your warranties.






Thanks to (in no particular order)

Rumon, Miwo, largon, Kyky, pinto, pitya

optional core voltmod points (thanks to Largon)

Okay so just simplifying here, All you need to do is solder a 500k ohm resistor inbetween those two points?

[slugzkea]

Okay so just simplifying here, All you need to do is solder a 500k ohm resistor inbetween those two points?

!bump

Electronics store closes in 2 hrs...

[LowRun]

Okay so just simplifying here, All you need to do is solder a 500k ohm resistor inbetween those two points?

Hmmm... I think you should do some more reading before going for the mod but here you go, VR from one of the green points to the blue point (which is ground), the two violet points are reading points as it says.

[slugzkea]

How about a pic of the completed mod? The diagram says one 500 k ohm resistor and indicates where to solder the ends (one is ground).

all i want to do is confirm that all you are soldering is one resistor?

[LordEC911]

How about a pic of the completed mod? The diagram says one 500 k ohm resistor and indicates where to solder the ends (one is ground).

all i want to do is confirm that all you are soldering is one resistor?

If you read the thread, it is suppose to be a 100k VR.
All you need is the card, soldering iron, solder, 100k VR, some wire, preferably double sided adhesive and a DMM.

[Unoid]

Pinto show us a pic of your mod, We want to see what points u used. What was your finally resistance value to achieve which vcore?

[nunchucka]

didnt do a volt mod but i used a modded bios and i got 815/2000 out of my 3850..

http://service.futuremark.com/compare?3dm06=4019858

used this bios: http://xxx.iax-tech.com/video/3800biosmod/01.htm

its screaming for more volts i reckon....

[tbone8ty]

so who is going to fallow through with pics of the vgpu mod?

and why are u guys ordering duo orbs? the zalman vf900 iis better IMO and u can control the fan speed.

just a suggestion.

[quake6]

vf900 isnt better than duo orbs...

[Cha0s]

i ordered a S1 Accelero and a 120mm cooler...für my 3850..and this is realy "cool" ^^ its better than the Zalman VF900

[Miwo]

Just a quick update:
Seems temps are holding me back from reaching full 1GHz stability atm. For instance, at 1.53v 1GHz core, I do not artifact in ATITool until I cross 50C. After a run of 06' my load temps are 55C. I've dropped the vcore down to 1.46v for 24/7 use at 945MHz Core. My load temps after 16hours is 48C, and at this setting it wont start artifacting until I hit above 60C.

My current cooling setup is an Accelero S1 w/ low speed 140mm Yate Loon. Sometime this week, I plan on replacing the Ceramique I used with Coollaboratory Liquid Pro and getting some more airflow across the fins by removing the black plastic caps on the S1. Hopefully that will let me do 1GHz for 24/7 usage on quiet Air

[K404]

A pic (using my uber1337 paint skills)

Please ask yourself...if you are unsure how voltmods work or how they should be attached....should you be trying the work? Remember- the responsibility for the mod lies with yourselves. If you kill your card, its YOUR fault, because the mods have been proven to work.

[largon]

If you read the thread, it is suppose to be a 100k VR.
(...)

100kΩ is about the minimum, higher valued VR allows minimum voltage as close as possible to stock but they also cause inaccuracy while tuning (larger granularity).

But yeah, 500kΩ might be a bit inconvenient.

[os008]

thanks. where can I find the variable resistor? Would radioshack have it?

Thanks!

Ryan

I don't know as i'm from Egypt, you have to ask someone who's from your country .

[Unoid]

how successful is the vmem for ocing?

[STEvil]

To keep from shorting the GPU voltmod you guys might also want to look at putting a fixed resistor in series with the VR... I would say a 10K fixed should do for most but it might be a bit high for getting 1.6v+...