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GPU Voltage Regulator Modification

The graphics chip voltage regulator is based on the dual-channel pulse-width SC1175CSW controller from Semtech. This time it works in the current sharing mode, when both channels serve one demand:

The nominal graphics core voltage on the PowerColor card is 1.7V.

We can increase the voltage at the output of the regulator by introducing an additional resistor. It is marked with blue in the scheme. I used a variable resistor with a resistance of 33kOhm, soldering it to pins 18 and 20 of the SC1175CSW chip. In order to prevent any regulator damage or graphics core damage by setting too low or zero resistance, I also switched on a “rescue” resistor with resistance of 1.5kOhm in parallel. You can see it in the snapshot:

 

After a few experiments with the output voltage of the GPU voltage regulator, I decided to stick to 1.94V value.

Graphics Memory Voltage Regulator Modification

After experimenting with the regulators on the PowerColor card, I found that the memory chips could only be sped up when the inner circuitry (VDD) voltage was increased, while tweaking the input-output circuitry (VDDQ) didn’t practically affect the overclocking results.

The VDD regulator in PowerColor’s card is an ISL6522 chip from Intersil. The typical connection circuit for this chip is shown below. I also marked the resistor, which resistance should be reduced to increase the output voltage:

For details, please refer to the description of the chip on the manufacturer’s website.

Again, I used an additional resistor with a resistance of 2.7kOhm, connecting it with wires to pins 5 and 7 of the ISL6522 chip:

 

Thus, I increased the output voltage of the regulator from 2.95V to 3.35V.

 
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