PowerColor RADEON 9700 128MB
This card was made from the RADEON 9500 following the well-known manipulations, so everything we say about the RADEON 9700 is also true for RADEON 9500-based graphics cards following RADEON 9700 design.
PowerColor RADEON 9700 128MB remains decently cool during work and its cooler is not very loud. Many other RADEON 9500/9700-based cards are similarly unpretentious, not requiring any modifications. In my personal case (in a system assembled from the Shuttle SS51G barebone) little noise from the PowerColor card turned to be quite noticeable, while the power consumption and heat dissipation of the card appeared higher than I wanted them to be.
Let’s get to business.
The graphics processor of the PowerColor RADEON 9700 128MB card is supplied with power through an impulse voltage regulator based on SC1175CSW controller from SemTech. This chip has two independent channels, set up for current separation in our case. The output voltage of the regulator is determined by the ratio of the resistances of resistors in the feedback circuit. All we need to do is to change this ratio in the desired way. It’s simpler to reduce the resistance of one of the resistors by attaching an additional resistor (if we were into extreme overclocking, we would shunt the other resistor).
The voltage regulator for the internal circuitry of the graphics memory chips (VDD) is based on ISL6522 chip from Intersil. The output voltage of the regulator, like in the previous case, is determined by the ratio of the resistors in the divider included into the feedback circuit. So our actions are absolutely the same in this case.
After reducing the voltage of the internal circuitry we should do the same with the I/O buffers (VDDQ). According to the requirements of the memory manufacturer (in our case, Infineon with HYB25D128323C-3.6 modules), VDDQ shouldn’t exceed VDD. The regulator of the I/O buffers of the graphics memory is designed on the same chip as the regulator of the internal circuitry.
The last onboard regulator is responsible for termination circuits (VTT) and, according to the specifications of the graphics memory chips, VTT must be half of VDDQ. This regulator is based on the same chip as VDD/VDDQ regulators, so you only have to find the necessary resistor on the PCB.
The snapshots below show voltage regulators of the VPU and memory (VDD/VDDQ/VTT) and exact locations where I soldered up additional resistors (I used trimming resistors with a resistance of 22kOhm).