Alright, you may be looking for some voltage mods. Below shows
you where to measure VGPU and Memory voltage with your multimeter.

*Take Note that all physical
Modifications Void your warranty!*

1 NVIDIA 8600GTS Overclocking!

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Default VGPU is 1.35v and default VMem is 2.1v

To get 1.4v VGPU, follow Step 1 and connect the 2 points with conductive ink.
To get 1.5v, follow up with Step 2, after doing Step 1, and connect the
next 2 points. I did not use the usual Feedback resistor mod since it induces overvoltage protection.

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To get more Memory Voltage, you can pencil resistor shown below, or solder a
20K ohms Variable resistor to point shown, with other leg connected to ground.
Set at Max 20K ohms, Decrease resistance to increase voltage.

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For even more VGPU, first remove the 5K ohms resistor and replace with 50K
ohms resistor as shown below. This will straightaway give you 1.65v, Without
the need for Step 1,2 mentioned previously!
For the Hardcore people who want to overclock to the maximum without being
held back by Overcurrent protection, you can remove a resistor marked below as
well.

6 NVIDIA 8600GTS Overclocking!