DDR4-2666 in DDR4-2133 slot: Slower than DDR4-2133 DIMM?
If a newer DDR4 DIMM (e.g.DDR4-2666 CL19) is installed in an older DDR4-2133 slot, will it be slower than a native DDR4-2133 CL15 DIMM, on account of timings being optimized for 2666MHz (e.g. CL19 > CL15) - or do the higher-MHZ-modules have a different set of timings for 2133MHz operation and will work as fast as older, native 2133MHz DIMM?
Re: DDR4-2666 in DDR4-2133 slot: Slower than DDR4-2133 DIMM?
JFYI there is technically no such thing as a 2133 slot. In regards to DDR3 and DDR4 it's actually the CPU that determines the memory speed, not the slot or motherboard itself.
Typically if you mix a higher speed part with a lower speed, the faster part will be forced to downclock to match the lower speeds. This means that the timing typically will be equivalent of each other, so they should perform identically.