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#11
the X.M.P. is actually an OC but not the one you are actually thinking.
also X.M.P. just makes it easier to configure your ram in just one simple menu selection (more fool proof), while without it, it's the job of the user to set the speed and timings of the ram correctly.
Memory is set to the lowest compatible frequency when first booted up into a new mobo, eg 1066MHz for DDR3. This is to ensure that your computer will boot up with the new ram. the X.M.P. just sets the ram to its rated spec, 1333, 1600, 1866, etc... within one step, which is essentially an OC, but not really as the ram is "rated" to run at such speeds/timings.