I have got similar combo - Ballistix PC8500 and Biostar TP45 HP. I have valid on 1400MHz 5,5,5,18, Dual Channel, 2,5V but Pi 1M is stable on 1398MHz I noticed that, increasing NB/SB voltage at this clocks give me more than vDimm. I don't want give more than 2,6-2,7V for my sticks, because I really like them