Hi, this is due to sub timings and cache hierarchy on SKL. To improve memory performance, tune the sub timings and overclock the mesh multiplier. You can try using Maximus Tweak modes and memory profiles available for the board within the UEFI. *
Most CPU for mesh will do a multiplier of 30 at between 1 and 1.15v, although be aware voltage to this rail will increase CPU temperature.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090