Actually I think I will do the VFB mod. 1.35V will be enough for me. If you want more, you should do the VSP-VSN mod..
On VSP-trace, there is one resistor which leads to GPUv. This is marked in the picture. There is also a place for another resistor VSP-VNS, which is not assembled. The VSP-GPUv resistor (lets call it R1) is currently very very small value, below one ohm. Like I said, it's most probably a 0R resistor. It should be switched to for example 100ohm. Then a resistor (or VR) between VSP-VNS (lets call this R2) could be assembled. These will form a voltage divider circuit, which would affect the output:
GPUv = VSP*(R1+R2)/R2
VSP will be the value set by VIDs (default max = 1.175V, unlocked bios = 1.2125V)
For example with R1 = 100ohm, R2 = 1500ohm resistor, VID set to = 1.2125V
GPUv = 1.2125V*(1500ohm+100ohm)/1500ohm = 1.2933V
I think the rule of thumb would tell you to use 20k VR. 20k VR set to max value (set to minimum voltage) would make the voltage:
GPUv = 1.2125V*(20000ohm+100ohm)/20000ohm = 1.2186V. 20k VR is quite fine.
More I think of this, more I want to do this mod
But the VFB mod is so much easier
By the way, about the VID pins. It looks as I thought in the first posts. Two msb VID's are not GPU controllable. I think the rest are. There is a pull-up resistors, but not for all VID's it seems... funny. Don't know whats going on there
It looks like VID6 (second most sensitive VID) is pulled up. Also on VID6 trace there are pads for another resistor. I bet this is for pulldown resistor. So it might be possible to make VID6 = 0 by moving the pull-up resistor to the other spot.Edited by Olper - 11/28/12 at 7:19am