Memory Voltage Modifications
MVDD and MVDDQ power are supplied via individual regulators. Two separate modifications are necessary for output voltage control over each power regulator group.
1 AMD Radeon HD 6970/6950 Voltage Modification Guide
It is necessary to first identify the two highlighted 0402-sized resistors; they should exhibit zero in-circuit resistance. Once removed, solder in the two potentiometers as described.
The resistance across points A and B, as well as points C and D, must be the minimal achievable by both potentiometers (0 ohm is preferable). You could substitute the 200 ohm potentiometers with 100 ohm parts if they are not available in your locality.

VDDCI Modifications
There are two ways to achieve VDDCI voltage increase. One involves shading a resistor; the other one requires a potentiometer to be soldered onto the Radeon HD 6900 PCB.
2 AMD Radeon HD 6970/6950 Voltage Modification Guide
For the pencil modification, shade on the highlighted resistor. Reduce the in-circuit resistance approximately 100 ohm at a time.
3 AMD Radeon HD 6970/6950 Voltage Modification Guide
Alternatively, solder a 100k ohm potentiometer across the highlighted points. Reduce in-circuit resistance approximately 100 ohm at a time.
Use either modifications to achieve your purpose – there is no need to perform both.
What sets this modification apart from the rest, is that all changes made to the potential divider network would affect the VDDCI output level only after the +3.3 V power rail has cycled. VDDCI voltage also increases in (presumably digitised) steps, rather than continuously, when effective resistance is reduced through either methods.
CAUTION: Do not adjust VDDCI “on the fly.”