This is a relatively simple mod with some soldering skills.
Parts needed:
1 10K pot (variable resistor)
Wire cutters/strippers (pocket knife works too)
2 wires cut to desired length.
1 soldering iron (35w or less recommended so as to not damage circuit board or solder pads)
rosin core solder.
Operation:
First, tin the leads of the 10k pot, and also both ends of the wires. You may also want to prep the legs of the IC to make a quick connection.
Notice I'm using a SMT pot. This was not by choice, this was all that was available at the time. A pot similar to the one used on the vgpu mod is preferred.
Make sure the pot is set to it's maximum resistance BEFORE attaching to the IC and powering on.
Anyway, after the pot and IC are prepped, solder one leg of the pot to pin 18, and the other leg of the pot to pin 20.
Power on the machine and read the vmem from the points shown in Illustration 2. The voltage is adjusted in the same way it is on the Vgpu mod. I turned the machine OFF before adjusting the voltage, however, it can be adjusted while the power is one...but it MUST BE DONE SLOWLY. I take no responsibility if you damage your card by adjusting the voltage while the power is on.
My default Vmem was 2.49v. I increased it to 3.01v. This enabled me to raise my ram speed from 325 (default, 650 ddr) to 371 (742 ddr).
Illustration 3 shows both mods installed.
Illustration 1:
Illustration 2:
Illustration 3:
