It might work, it might fail.Consider a mobo which supports a specific ram speed, but what if you plugged a memory having higher mhz tgan that specific
For ddr3, it should clock down no problem and still work. ddr4 is too fickle to guess.Its gonna be okay, it will just downclock the ram to the speed that the motherboard supports, BUT if the motherboard was DDR3 it wont support DDR4, they must be the same, and DDR4 wont support DDR3 too.
Never tried that but, i heard many techs says it wont work.For ddr3, it should clock down no problem and still work. ddr4 is too fickle to guess.