This is quoted from overclockers.com. As a reminder of interesting tech implemented in my corsair vengance ddr3 stick.
XMP (Extreme Memory Profile)?
Is basically a non-JEDEC approved SPD table for your RAM that is programmed into the sticks. By setting XMP you can run the sticks at their RATED speed and timings even if it requires more vDIMM to do so.
1333 MHz 9-9-9 @ 1.5v is JEDEC standard
Most kits will do 1600 9-9-9 at 1.6V
To get your system to set that automatically you need an XMP profile and a board that is capable of utilizing it
No memory IC company in the world AFAIK actually makes 1866MHz or 2133 MHZ ICs. (I believe some make 1600 now) they are all set from the manufacturer of memory modules)