Faster memory will clock down to run at optimal speed depending on processor model installed.
Registered RDIMM, Load Reduced LRDIMM, and Unbuffered UDIMM memory modules CANNOT be mixed within the same system. This system supports both ECC and non-ECC memory. Mixing ECC and non-ECC modules is not recommended.
Mixing x4 and x8 modules is allowed, however not within the same bank.