Guide To Volt Modding A 7900GT

PogMoThoin

Disclaimer:
I'm not responsible for anybody frying their gpu. Do this at your own risk. I also wouldn't recommend this on the stock cooler. You also need a good quality psu.


The 7900GT operates at a stock voltage of 1.2V, connecting any or all of the coloured dots in the pic to ground increases the voltage by painting a conductive line with a conductive pen. There are several mods, 1.25V, 1.3V, 1.35V, 1.4V, 1.45V, 1.5V & 1.55V
I chose to do the 1.5V mod as this is what the chip is actually rated for and nVidia have it underclocked to 1.2V. The best thing about this mod is that it can easily be reversed & is not permanent.



More info on all the mods:
http://www.planetamd64.com/lofiversion/index.php/t21181.html
http://sg.vr-zone.com/?i=3330&s=2
http://www.vr-zone.com/?i=3437&s=1

Before:

I've had my 7900gt oc'ed to the maximum i could on stock voltages. If i went any higher i got crashes in 3Dmark. Here are my before settings & temperatures:



idle temp: 38'
Load temp: 52'

3DMark05: 10672: http://service.futuremark.com/compare?3dm05=2236197
3DMark06: 6067: http://service.futuremark.com/compare?3dm06=522108

Memory Mod:

To do the volt mod you need a multimeter & a pencil. Gently shade the resistor in the pic below (marked VMem) until you reduce the resistance from 608 Ohms to 553 Ohms. This is tricky as you need a steady hand to touch the ends of the resistor with the multimeter probes.



Volt Mod:

Using a conductive pen, connect the points in the pic below. I had to remove the metal plate on the top of the gpu to get room for the paint. I got my sis to buy the conductive pen for me in NY as it was E40 in Maplin.
http://www.radioshack.com/product/index.jsp?productId=2104395&cp=&origkw=circuitwriter&kw=circuitwriter&parentPage=search



This is very tricky & will take several attempts to get right. Make sure you have acetone & a cloth ready. I practiced drawing lines with the pen on a piece of cardboard first, & still had to rub out & start again about 6 or 7 times.



Results:



Idle temp: 41'
Load temp: 72'

3DMark06: 7054: http://service.futuremark.com/compare?3dm06=527383
3Dmark05: 12386: http://service.futuremark.com/compare?3dm05=2241811

Quite impressive, don't you think . Of course i'm not gonna leave my clocks up that high & have them dropped to 700/885 for everyday use. I also added 2 heatsinks to the back of the card as in the pic below. Sorry bout the bad quality, i'll update it later.




I also had to turn off driver testing in Rivatuner to allow me to clock higher. You do this in Power User in the overclocking\ global settings section.

Good Luck

awhir

very cool .

also your sigs only a tad bit to big oh and were did ya do that photo shop.

PogMoThoin

awhir wrote:

also your sigs only a tad bit to big oh and were did ya do that photo shop.

:rolleyes: I'm no good at that photoshop sh1t, don't even have photoshop, fella on DFI-Street did it for me. Might reduce it later.

awhir

can ya give me his name pls m8 and also its a great gob there on the card.

oh and when i get the old pc running agian:( will give ya a game of css,bf2.

PogMoThoin

His names s1ick, does a good job, but there's a few others over there making them to order. Only posted yest & had it done for me when i got back from work 2day. Post in this thread; http://www.dfi-street.com/forum/showthread.php?t=34554

Is this sig size better? Harder to read, big size looks ok on other forums with custom avatars.

I've not been playin last few days, been sick for few days last week & then moddin & clockin gpu. Bad bout your gpu, got 6800 i can loan ya till ya buy 1 if ya strapped for cash, be up that way on sat.

awhir

na its my mobo i think or psu not givin the gfx power.

Anti

excellent stuff, as i just bought a 7900gtx, hopw it works the same, will fond out

awhir

dont think you can volt mod a 7900gtx.oh and i thought you bought a 7950.

oh and weres your new core duo pc you were buildin>>>????

i need answers people.

PogMoThoin

AFAIK you can mod a gtx, follow the links at the top of the post. Good luck.

Anti

awhir wrote:

dont think you can volt mod a 7900gtx.oh and i thought you bought a 7950.

oh and weres your new core duo pc you were buildin>>>????

i need answers people.

The 7900gtx is for my 3500+ i got it off ebay for a nice price

Im still building the core duo, but im a bit short on cash, so i had to cancel a few parts

But this months pay check should have a nice whack of commision. so hopefully ill have it up in a few weeks

ongarite

I've done this volt mod on my Evga 7900GT already. It must be on the easiest mods every on a video card. I presume you have changed your heatsink of the gpu as the stock small one won't handle 1.5V. I have a Zalman VF-900Cu installed on mine. Really good temperatures and very quiet.

I have my 7900GT running at 670MHz at 1.5V and memory at 900MHz at stock 2V. I would be more wary of the memory pencil mod as its a bit risky and the 2.2V mod doesn't always lead to a speed increase.

Anybody know if the 7950GT is also modable like the 7900GT??

PogMoThoin

ongarite wrote:

Anybody know if the 7950GT is also modable like the 7900GT??

:rolleyes: Dunno, look foir a pic & compare the boards to see if they look similar. 7950 is supposed to be just an oc'ed 7900, not supposed to be any other changes.

Also i definitely wouldn't recommend this mod on the stock cooler. I said so at the top of the guide.

L31mr0d

Ok so I got myself a 7900 GT 512mb and i'm itching to do this mod. Firstly where did you get the heatsink from, is it just a NB heatsink? Is it actually needed for this mod? Also what is the other option you have for the dropping the resistor value? Does that say to add a 10k resistor in parallel with it or something? Also what is the VGPU measure and VMem measure are these just points for the multimeter when the card is running?

Anti

i pussied out

I dont wanna **** this card over. Plus its fast enough at stock for me.

L31mr0d

Hey Pog, fancy throwing your conductive pen my way ? I'll pay for posting or whatever and a quid or 2 for its use. I only need it to draw one line.

PogMoThoin

L31mr0d wrote:

Ok so I got myself a 7900 GT 512mb and i'm itching to do this mod. Firstly where did you get the heatsink from, is it just a NB heatsink? Is it actually needed for this mod? Also what is the other option you have for the dropping the resistor value? Does that say to add a 10k resistor in parallel with it or something? Also what is the VGPU measure and VMem measure are these just points for the multimeter when the card is running?

The heatsinks i used were the type that come with the zalman cooler. I had some old ones. They're not needed 2 do the mod, ya can add them later. These chips get very hot when modded.

I didn't use the Vmem & vgpu measure points, i just measured across the Vmem resistor and kept shading in the resistor until the resistance dropped to 553ohms. This is all you need the multimeter for.
Just follow the voltmod pic for the 1.5V mod. I didn't measure, I just took their word for it.
Good luck
Pog

Edit: pm your address & i'll post