fgw,
Shall do that mate and get back to you.
I just finished reading and re-reading the Intersil ISL6327CRZ multiphase closed-loop feedback and compensation PWM Voltage Reg datasheet, the VR used by NV in the die shrink G200 reference cards, GTX 260 55nm and GTX 285 55nm.
Seems NV screwed you guys over with VR cost cutting this time around, mind you the IC itself only costs $5usd or so.
It's a VR designed with cost savings and affordability in mind so it lacks any kind of external low-pin count bus interface accessibility and relies on the pcb designer to set up all the necessary operational values in design and testing phase. There are 8 VID pins which when pulled up the base VID is read by which pins are 0 or 1 and converted to digital signal by DAC. '
Voltage adjustment is done through current offset via the OFS pin, which is polarity dependant for negative or positive offset, switch to Vss (gnd) for neg, switch to Vcc (vin) for pos. Offset is configured through external resistors connected between the DAC and REF pins, the impedance dynamically controls the current which in turn determines the Vout (voltage out).
Long story short, unless NV have some kind of low pin count programmable interface to adjust a pull up or pull down resistor connected between DAC digital VID signal pin and REF voltage reference pin there is absolutely NO CHANCE AT ALL to control Voltage Adjustments via software on either the GTX 260 55nm or GTX 285 55nm. The only way would be to change the resistor between DAC and REF pins, to give a greater current offset to drive Voltage out higher.
If EVGA is saying it is possible on their cards, short of physical changes to the NV reference cards to add this basic functionality I can't see how it is possible at all. I read over the datasheet a good 4 or 5 times just to make sure I completely understood the electrical design and don't see any way to do it.
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