Radeon HD 4850 Voltmods
GPU Voltage Mod (soldering)
GPU Voltage Mod (pencil)You have to do only one of those mods, depending on the voltage you want to achieve.
This first voltage mod is easy to do but will not give you much more than about 1.4V on VDDC.
If you need more than 1.4V you should do above voltmod. Please note that you have to paint on the PCB between the two solder dots. Since this is more difficult we recommend the first pencil mod for smaller voltage increases.