Registered ECC (RDIMM) vs Unbuffered ECC (UDIMM): RDIMM is required for dual-socket setups

Unbuffered ECC won’t work in dual-socket LGA2011 boards with Xeon E5-2670 — the memory bus can’t handle the load. Registered DIMMs have a buffer chip that lets both CPUs talk to memory reliably. For a dual E5-2670 server, just grab cheap 16GB or 32GB RDIMM sticks; UDIMMs are only for single-CPU workstations.