Before we started on the voltage modification, we picked out a the measuring points for the memory voltage. Vmem can be read off the highlighted end of the inductor in the “SMPS A601-00A TILE” area. The reading is taken with respect to ground.

vrmmem Voltage Modification Guide For Sapphire X1600PRO 256MB

The default Vmem hovers around 2.06V.

Flip to the back of the card where the voltage modification is carried out. You will see a PWM Buck Regulator going by the part number of RT9232.

 Voltage Modification Guide For Sapphire X1600PRO 256MB

Hook a 50kOHM variable resistor between pin 5 and ground. Starting with the resistance set at maximum, decrease the resistance slowly for Vmem to rise.

VTT tracking is automatically acheived via the RT9199 Termination Regulator.

 Voltage Modification Guide For Sapphire X1600PRO 256MB

There is therefore no need for further VTT modifications.