I have been having with the two sticks of 1600 MHz DDR3 in my Supermicro X9DRL-3F. For some reason, the memory runs at 1333 MHz regardless of whether it is forced to run at 1600mhz in the bios or not.
It might relate to the voltage; For DDR3 1600Mhz, it must be 1.5V, if it’s 1.35V then it won’t run @ 1600 MHz