7900GT Voltmod-2

[t024484]

I have tried to bundle all the wisdom of previous mails in the pictures plus the explaination below.



Resistor "J" is a 5Kohm resistor, and causes the Core Voltage, Vgpu, to be 1.2Volt in the unmodified situation.
Replacing this resistor with a 50Kohm resistor, changes the Vgpu to 1.5Volt.
In the picture hereafter, you can add to this voltage, thus being 1.2 or 1.5Volt, another .05, .1 and .2, either as a single step or as a combined set of steps.
So your options are: 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5 or 1.55Volt
and with the 50Kohm mod: 1.5, 1.55, 1,6, 1.65 and 1.7Volt as a maximum.

Resistor "H" measures 3.5 Kohm, and controls the Over Current Protection.
If you suspect the OCP giving you trouble, you can double this resistor to 6K8 Ohm. I had no problems, so you can probably leave it as it is.

Resistors "I" are said in the previous thread to disable the Over Current protection . THIS IS NOT THE CASE.
These resistors. measuring 1,8Kohm, are meant to balance the current between the two pair of switching Mosfets to carry an equal amount of load.
Leave them, or replace them with values of 3,9 kohm which should only be done if you are having mysterious problems.

And than comes a very important Mod, being resistor K.
This resistor measures ca 80Kohm, and sets the switching frequency.
Connecting a 100Kohm resistor in parallel, almost doubles the switching frequency, and solved my problems completely.
You could eventually do this mod by pencil, try to get the value down to approx. 45Kohm.

The next picture shows the Mods to change the 1.2 or 1.5 Volt to a higher value.
C gives 0.05 Volt increase when shorted to ground
B gives 0.1 Volt increase to ground and
A gives 0.2 volt increase to ground,
Plus any combination of A, B and C.



I have given two possible routes to achieve your Vgpu increase.
Use either the upper or the lower set of traces.
When you only use the red trace, you will have 0.05Volt increase. (1.25V or 1.55Volt)
When you use Red plus Yellow, you will have a 0.15Volt increase (1.35Volt or 1.65Volt)
When you use Red, Yellow plus Purple, you will have a 0.35Volt increase ( 1.55Volt, do not use it in combination with the 50Kohm resistor mod)
Of course you can also connect a single point to get what you want, f.i. ground point C (sorry for the earlier typo) to get 1.4Volt.
Although a bit more difficult to achieve, it is still doable.
Go with conductive ink with a large U around all the other points towards ground.

You can either do the modding with a thin wire and solder, or with conductive ink.
Do not worry about all the points between C and B, they are not connected to anything, and are used to keep the lines as simple as possible.

Look at the bottom of Page 22 of this thread for an even easier way to do your voltmodding.

Also have a look at the bottom of page 20 for the possible addition a 47Kohm resistor, giving the system a higher stability

I have republished the expired Pictures on Page 26, posting nr 640