Faster memory will clock down to run at optimal speed and voltage depending on processor model and number of modules installed.
Due to chipset limitations, Quad Rank memory will operate at 1066MHz in the first bank. Adding Quad Rank modules in the second bank will operate at 800MHz.
This system supports either Registered ECC or Unbuffered ECC memory. Mixing Registered ECC and Unbuffered ECC modules is not supported within this system.