all vmod for all 6800

[acdc]

Hi everyone,
I've read the vmem voltage mod guide for 6800GT/Ultra in VR-Zone, but i have some notes and I'd like to warn 6800 ultra's users - Don't make this mod because it will easily damage the memory! This guide is right for only 6800GT, but not for 6800Ulta, because its memory is made with different (from 6800GT) power distributions. Nvidia set for ultra 2x Voltera's VT223 PWM chips (in contrast to 6800GT where there is only one - the second is missing) but their outputs don't share power! Every PWM distrubute power for two pairs of memory chips - half of the memory. I don't know what's reason NVIDIA engineers to set separate power in pair, because one of Voltera's VT223 basic features is to connect two or more chips in shared outputs as master and slave to distribute more power.
For the right mod of ultra, it is necessary to change resistanse of two resistors (in contrast to GT where there is only one and its see in the VR-Zone guide) with the same value - 43KOhm for 6800U reference design. Each of this resistors determines the voltage for 2 pairs of mem chips, and for this reason there will be two check points - in contrast to the 6800GT where there is one checkpoint because only one PWM Voltera's VT223 is set and it distributes power for all memory chips.
I have eVGA 6800 Limited Edition (The same PCB and components that Ultra), but for me this mod makes the memory unstable. I don't know why it happens, but i think it is due to a problem in the distribution of the proper Vref (Vref=0.7Vddq) that DDR3 requires.
In the pictures below you can see the second resistor marked in violet, and the check points are in the same colors as the resistors.