View Full Version : Working Vmod for 7900GT

03-23-06, 10:05 AM
A member of xtremesystems.org named SF3D figured it out.

He replaced the 5K Ohm resistor that is connected to the pin 1 of the ISL6568 regulator chip for a 50K Ohm resistor. This caused the ISL6568 to use a different voltage table and now the VGPU is 1.5V.



03-23-06, 01:25 PM
WCed GT at 705/1800, perfectly stable. :eek:

03-23-06, 03:14 PM
There are another idea, like to stick one end of wire right between pins #21 and #22 of the ISL6568 regulator chip (U502), and get 1.4V VGPU right away.

03-23-06, 03:30 PM
Or solder a wire from pin 32 to pin 30 and 31
AND a wire between pin 22 and pin 21 to get 1,55V

03-23-06, 03:44 PM
Lol. I dont understand any of that article.

03-23-06, 05:26 PM
How about being greatful and liking the bloody card.... whats wrong with that?

I love the tech tweak enthusiast, blowing crap up all the time...its entertaining.

03-23-06, 09:55 PM
From 1.2v to 1.5v... hmm i wonder how long that'll last.

03-23-06, 11:08 PM
I would consider doing this, but the card is damn nice as it is. any idea on how this will effect and sli config if you do it to both cards?

03-24-06, 01:49 AM
Oh cool, let's bet on how long until the first "My 7900GT is dead" thread...

03-24-06, 05:44 AM
No worries. The 7900GT cores and the 7900GTX cores are identical.
7900GT default 3D voltage: 1,2V
7900GTX default 3D voltage: 1,4V

So the 7900GT is actually under-volted from the start.
Computer equipment usually have at least 10% safety-margin when it comes to voltage. Using this rule, 1,54V is probably safe enough.
The 7900 series uses 90nm production technology. Same as Venice (Even if the production techniques are a bit different). Venice is "safe" up to about 1.5V. 1.55V is pushing the limits of limited returns and 1.6V...well...
Using this comparison, 7900 series should be safe up to about 1,55V.

You obviously need better cooling to play safe though.

Say you overclock from 450/1320 to 590/1750 with stock voltage and cooling. A decent overclock.
Now you bump the Vcore to 1,55V and increase the Vmem as well. Suddenly you have a card running at 730/1850 perfectly safe. Who wouldn't want that? ;)

Oh and BTW: No card(s) are ever fast enough. That's just the way it is. Try running Oblivion maxed out with above 60fps all the time. You can't do that even with 7900GTX Sli'ed. In other words: the cards are not fast enough... :D

03-24-06, 06:02 AM
^^^ Very true. Now if I just had the balls to risk that on 300 hardware. lol

03-24-06, 06:35 AM
well there is always an rma!!!!!!!!

03-24-06, 06:38 AM
Wow thats nuts!

03-24-06, 06:43 AM
well there is always an rma!!!!!!!!

I meant the vmod itself. Im not good with soldering such tiny things. If the card blows after a week, well thats tough luck, but definitly no reason for me to RMA it. You risk, you pay.

03-24-06, 11:03 AM
The 6800GT cores were identical to the 6800Us, look how many of those died though.

03-25-06, 12:33 PM
The easiest and fastest way to get 1.4V VPGU on the 7900GT is using conductive ink as shown in the picture in the below link.


1.4V is the GTX default voltage, so if you are lucky and got a good quality G71 core, you can reach GTX speeds with this simple Vmod. But, a better cooling solution is a MUST.

03-26-06, 12:53 AM
The 6800GT cores were identical to the 6800Us, look how many of those died though.

bump for this!

Won't the 7900GTs that are volt modded just die the same death that the 6800GT did?

03-26-06, 12:56 AM
There is alot more to a video card than a core and memory.

The 6800GT's failed I believe, because of the VReg's. They were just not designed to take that type of voltage.

I haven't seen any indication that the 7900GT is using the same components, capicitors, vreg's, etc. as the 7900GTX, so, I would advise to be careful when doing a mod such as this.

03-26-06, 04:07 AM
This mod is "cleaner" than most though, I think it's safe to bump it to at least 1,4V (default 7900GTX voltage). I've V-modded all my videocards from my 9700Pro to the two 7800GT's I just sold. All of the cards are still working.