Need o.c help

I've been able to be stable everything auto (vcore 1.37) up to 48, but can't get 49 stable with vcore up to 1.40, windows failed during the first intel burntest, I get a multicolored screen but no bsod. My cpu pll overvoltage is enable and llc set to level 1. All other features are disable. I only manually change the vcore, all other voltage leaved to auto.
Any Idea or I just have a not so good chip.