This guide will show you how to measure the GPU voltage and increase the voltage through resistor or pencil to improve overclockability.
Look for the chip at the back of the card as shown. You can measure the voltage
of your 6800 ultra from the point shown below. Without drivers loaded it should
be around 1.13v with drivers loaded it should be 1.43v. To increase voltage,
you can solder a 100K variable resistor to the point shown.
Set the VR to the max 100k ohms first. Ground the other end of the VR. This
will give you around 0.24v more, so 1.37v without drivers and 1.67v with drivers.
There is overvoltage protection on the card so that as you turn down the VR,
there will be a point whereby it will drop voltage and throttle with lines on
screen. My card is insulated at the moment so I have no chance to check for
You can also pencil the resistor shown to increase voltage.
Original resistance is around 8K ohms, do a very light pencil job and take
it to around 7.4k ohms or so for the maximum additional of 0.24v. As the resistor
is high resistance, even a bit of pencil stroke can drop resistance by a lot
so measure resistance before turning on.
Lastly, for additional 0.1v you can flash your card with this bios
modded by Mr xtremetheme. This 0.1v will come in after drivers are loaded.
So you now have about 1.77v for overclocking, as compared to 1.43v stock. Now
that the voltage is there, for the extreme coolers you will still need to deal
with the cold throttling set by NVIDIA, once the core temperature goes below
25C in the thermal settings tab, the safety indicator will shoot up to red hot,
So extreme coolers will have to find their way around this. Right now, xtremetheme
is also looking for help to mod a bios to over-ride this throttling issue and
the thread can be found here.
This applies for both AGP and PCI Express Cards!
Discuss about overclock results and cold throttling workarounds here in our
For the VDDR mod, you can refer to