Why Does XMP Have Two Profiles?
Most manufacturers provide two profiles for DRAM. The first, or specification profile, adheres to the base timings as sold. The second profile is generally aimed at enthusiasts and is a little more performance-oriented, but these tighter timings might not be stable in certain configurations. Often, this is a tighter command rate, as pictured below. The command rate often needs to be increased as additional DIMMs are added.
Some DRAM with aggressive XMP profiles provide a slower secondary profile to increase compatibility, as an intermediate step between default and rated values.