Once I changed to the f6a bios 53 was not really a problem though my board runs only single channel from day one and is being replaced. I got my rma from gig which is cool and have another ud5 coming from another source even faster. I will keep testing on this board until new one arrives. I started at 1.575v cpu and worked backwards down to settle on 1.475v stable. Ram is Gskill 17066 Pi which runs either Auto XMP profile one at 2134mhz or disabled with any speed combi up to 2155 at 101 bclk. Reducing bclk below 100 is sometimes needed depending on chip quality. My 2600K needs 1.5-1.55v for 53-55 range, 56 needs 1.575v.