Hey Krich, I'll see if I can give you a hand. First, I don't have a Quad so your ahead of me there. I can give you a couple suggestions you can see if they help or not. Until you get some stability at the higher speed set the ram timing to 5/5/5/15. Change it back later. The vdimm seems a bit high as well. I know that is good ram but I don't know if it needs that much esp. at this speed. For 1.4vtt, your mch ref seems high also. By a fair amount. Have you tried increasing the PLL to 1.57v when you try to boot at 4.3 or above? All these things on mine need to be "together". It takes some time but when you get things closer maybe you can get a bit lower vcore. Maybe someone with a Quad can help with your mch core or something relating to what I mentioned.