4600 CL15 with 1.7375v DRAM, and 1.3v IO & SA. Also 5.3 Ghz all cores on my 10900K. Actually it errored on another longer run I was trying at around 12 mins, so I'm back up to 1.75v. Disclaimer - dont run voltages like these on most other ram sticks, these are Micron B die single rank and can handle as such. You can get these high end DDR4 rams for cheap now, its a worthwhile upgrade if you are still on under 4000 Mhz stuff and can either sell or reuse your old ram in another system as I will be doing for my lounge PC.