Extreme Overclocking Experience Step 1: Pulling Up the GPU Voltage
GeForce FX 5950 Ultra (and the previous model, GeForce FX 5900 Ultra) uses an ISL6569ACR controller chip from Intersil as the GPU voltage regulator. This chip features an intellectual option of adjusting the output voltage “on the fly” through changing the state of the digital inputs (VID0…VID4). I discussed the chip in detail when I carried out extreme-overclocking experiments with GeForce FX 5900 Ultra (see our article called Extreme Overclocking Experience: NVIDIA GeForce FX 5900 Ultra against ATI RADEON 9800 Pro).
EVGA e-GeForce FX 5950 Ultra of course uses the additional features of the regulator. The GPU voltage is not a constant value by the EVGA card: it is equal to 1.1V at startup, 1.2V in 2D and 1.6V in 3D modes.
To increase the core voltage, I used the same OFS input of the controller chip as I did with the GeForce FX 5900 Ultra:
According to the documentation, when there is a resistor with a resistance R between the OFS input and the “Ground”, the output voltage of the regulator goes up by V=(R*100mkA)/10.
So that’s what I did. The red arrows in the snapshot below point at the spots where the resistor with zero resistance originally stood (by default, the OFS input is grounded and the bias voltage equals zero):
I soldered up a variable resistor with a resistance of 22KOhm instead of the zero one. By increasing its resistance I could raise up the GPU voltage. I preferred to stop at 10KOhm, which resulted in an increase of 0.1V for the GPU voltage in all operational modes. In other words, it was 1.2V at startup, 1.3V in 2D and 1.7V in 3D modes. That’s how we dealt with the GPU. Now it is the memory’s turn.