Nvidia GeForce 6800 Ultra Voltage Mod with Pencil

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VR-Zone's resident hardcore overclocker, Shamino, has thrown up a new Guide to Modding your GeForce 6800 Ultra voltage through resistor or a humble pencil to improve overclockability.

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, like this.

Source: Vr-Zone