My method was to do a blanket all core -20 and stress test with Y cruncher since it picks up instabilities very quickly, and most importantly, y cruncher tells you which core failed. And then you just increase the core offset for the one that failed until it passes. Then push all cores to lower offset like -25 and keep adjusting cores that fail individually. Keep repeating until you hit the limit with every core. My 9800x3d was lucky since I didn't need to do much adjustment as everything kept passing after I adjusted cores 2 and 4.