Keep your RAM voltage within .5 of your VTT. Yours I believe is like you posted, QPI/VTT Voltage. Keep it within .5 of that. Some mobos won't allow for you to go outside this safe range, I don't think yours will so be careful. I have pushed my RAM upwards of 1.85v. I have some Hyper Elpida's. All depends on the RAM and cooling. Mine was on air with a 120mmx38mm San Ace fan blowing across them.
So if you are at 1.85v RAM your VTT needs to be 1.35v or higher foe example.