We have your X9DAi board and use 2 CPU & 8 sticks of 4GB Crucial DDR3 1600Mhz ECC unbuffered EAM, but it only shows running at 1333, is there a BIOS setting to change to 1600 full speed?
No, with this configuration, you can only run at 1333. To run at 1600, please use registered DIMM. You can check:
http://www.supermicro.com/support/resources/memory/X9_DP_memory_config.pdf