X-bit labs

eVGA e-GeForce FX 5950 Ultra and PowerColor RADEON 9800 XT: Extreme Overclocking and More! (page 4)

Category: Video

by Tim Tscheblockov

[ 01/04/2004 | 09:43 PM ]

Extreme Overclocking Experience Step 2: Increasing the Graphics Memory Voltage

An impulse regulator on the HIP6012CB chip from Intersil supplies power to the internal circuitry (VDD) of the graphics memory chips. The chip is connected as shown below:

The output voltage of the regulator is defined by the resistances of the R2 and the R3 resistors according to the formula: V=1.27*(1+R3/R2). To boost the regulator’s output voltage, we can reduce the resistance of the R3 resistor (marked in red in the scheme) by soldering up one more resistor in parallel to it.

I used a 5.6KOhm resistor, having soldered it via wires for convenience. The orange arrows below show where the additional resistor is:

This modification helped me to increase the voltage of the internal circuitry of the memory chips from 3.2V to 3.44V.

Input/Output circuitry (VDDQ) is power-supplied by another regulator, based on the ISL6225CA chip, which was specifically designed for work in memory voltage regulators. The output voltage for each channel of this dual-channel regulator is determined by the ratio of resistances in the feedback circuit. This is a simplified scheme of the chip:

The output voltage is determined by the formula: V=0.9*(1+R1/R2). We can increase it by reducing the R2 resistance (as marked in the scheme above).

Having found the necessary resistor on the PCB, I attached an additional 4.7KOhm resistor to it. It is marked with orange arrows in the snapshot:

As a result, the voltage of the I/O circuitry increased from 2.53V to 2.88V.