Recently my laptop's motherboard died. So I have spare SSD, HDD and RAM sticks lying around.
I want to buy a i3 NUC8I3BEH and use my old RAMs which are rated at DDR4-2133Mhz. But NUC8I3BEH specs says it needs DDR4-2400mhz RAM. Would it be possible to use DDR4-2133Mhz RAMs into the new NUC?
The safe way to go, is to buy memory validated by Intel for this NUC. On the List of Intel Validated memory Modules for NUC8i3BEH you will find 2133MHz SODIMM. However if you bought already memory, which is not listed on this list, but meets the requirements, it still should work.