Hi All, I'm really struggling here. I've just purchased some Corsair DDR3 Vengeance Pro Series Red DDR3 Memory with the Specs CAS 12-13-13-35, 1.65V at 2666MHz. I got 2 sets (2x4GB per set, 16GB overall, all 4 slots are occupied). When I choose the XMP profile, the computer fails to post, it resets and then tells me "overclock failed". To get it to boot I set the speed to 2133MHz and it is now stable. MoBo is an Asus Maximus Vi Hero (Z87) and a Haswell Core i7 4770K with a H60 closed loop on it. Power supply is a Corsair AX750. My question is, why can I not hit the advertised speed of 2666MHz? Do I need to send more voltage through them? Thanks for your help in advance.