Hi newcomer and welcome to the Tom's hardware forum.
Your RAM don't run at full speed beause your mobo don't support that speed by default. If you want that your RAM run at that speed, you need enter to the BIOS and set all the specifications of your RAM manually. The CL, voltage, tRCD, tRP.... If you want learn more about RAM timings, read THIS
is for DDR and DDR2, but is the same for DDR3.