Get registered ECC (RDIMM). Unbuffered won't work.

Not for dual-socket. The Xeon E5-2670 can technically use unbuffered ECC, but only in a single-CPU setup. The moment you add that second processor, the memory controller demands registered DIMMs. Most dual-socket LGA2011 boards won’t even boot with UDIMMs installed.

The why is boring electrical stuff: unbuffered sticks put too much load on the memory bus with two CPUs. Registered modules have a buffer chip that offloads that, letting both processors talk to memory reliably. It’s not a preference thing – it’s a requirement.

If you’re building a dual E5-2670 server, just hunt down cheap 16GB or 32GB RDIMM sticks. They’re plentiful because nobody wants old server RAM anymore. Your motherboard manual will also scream “RDIMM only” for dual-CPU configs.

Don’t overthink it. Unbuffered is for single-CPU workstations. Registered is for dual-socket.