I have 3 X58A-UD3's rev 2.0 running at the moment and in my experience I estimate they are all undervolting the QPI by .05-.07v so if you set 1.35v in the bios then the real voltage is only 1.28-1.29v.

This is the same on the FA and FB bios...

I do not know the QPI read points (feel free to point them out if anyone knows the location ) so I cannot confirm but the chips run stable at 1.275 QPI on other boards that I have measured with a DMM and they require 1.35 set in bios minimum for stability at the same clocks on the Gigabytes...