LRDIMM vs RDIMM

LRDIMM, short for load-reduced DIMM, is a registered DIMM with an extra isolation buffer between the DRAM and the memory bus. RDIMM, or registered DIMM, buffers only the command and address signals through a register chip. Micron says the LRDIMM buffer cuts the electrical load on the bus, which allows more memory per system. Micron positions RDIMM for balanced performance and cost, and LRDIMM for maximum density. Also written LR-DIMM.

Supermicro's X11 guide covers DDR4 boards for 2nd Gen Intel Xeon Scalable processors. With 16 Gb DRAM it lists a dual-rank x4 RDIMM at 64 GB and a quad-rank x4 LRDIMM at 128 GB, both at 2933 MT/s with one or two DIMMs per channel. The 3DS versions reach 128 GB at two-high and 256 GB at four-high. The guide forbids mixing LRDIMM and RDIMM in a channel, across channels, or across sockets. Supermicro's X14DBI-T, a Xeon 6 board, lists RDIMM up to 128 GB, 3DS RDIMM at 256 GB and MRDIMM at 32 GB and 64 GB.

Order LRDIMM only when the board manual lists it and the capacity target needs 128 GB modules on DDR4, where non-3DS RDIMM stops at 64 GB. Otherwise order RDIMM, and fill the whole system with one type.

Sources

Last verified October 30, 2026.