Discussing CPU upgrades.
Discussing CPU upgrades.
Is the 1866 DDR4 model currently available for consumers? The fastest I've encountered is 2133 from Skylake's initial launch. It seems you likely didn't turn on DOCP or your processor doesn't back that memory type, which isn't surprising when comparing to Zen 1.
You're likely checking the speed shown by software in the operating system. The base speed for DDR4 is 2133 MHz, so you probably don't need to upgrade your memory.