RDIMM vs UDIMM vs LRDIMM: Identify What You Have

By The Founder · Reviewed July 7, 2026 · About the author

The 10-second identification

Look at the center of the module between the DRAM chips: a small extra chip there means RDIMM (registered — one register chip) or LRDIMM (load-reduced — a larger buffer plus data buffers along the bottom edge). No extra chip: UDIMM (unbuffered, desktop) or SODIMM (the short laptop form).

Label shortcuts

The label usually says it outright: Samsung/Hynix/Micron codes include R for registered, LR for load-reduced, U/E for unbuffered — and "PC4-23400R" ends in the type letter. Full decoding in the label guide.

Why it matters to your payout

They are not interchangeable and they price differently: a 64GB RDIMM and a 64GB LRDIMM live in different rows of the Payout Index. Server boards want R/LR; desktops want U — which is why "64GB of DDR4" is never enough to price.

ECC myths

ECC UDIMMs exist (workstation boards), non-ECC RDIMMs effectively do not; ECC does not make desktop RAM server RAM; and ECC-vs-non-ECC is visible as 9 chips per side instead of 8. When in doubt, paste the part number into the quote form — matching it is our job, not yours.