RDIMM, LRDIMM, or UDIMM? ECC or not? Which generation? Here's how to read a memory module in about two minutes — and why each detail changes what it's worth.
Two sticks of RAM that look identical can be worth very different amounts. A 64GB DDR4 LRDIMM and a 64GB DDR4 RDIMM are built differently, sell into different systems, and carry different prices on the used market. Before you request a quote — or decide whether a pile of pulled modules is worth shipping — it pays to know exactly what you're holding. The good news: everything you need is printed on the module itself.
Almost all enterprise memory falls into one of three types. The difference is how the module buffers the signals between the DRAM chips and the CPU's memory controller.
No buffering between the chips and the controller. This is standard desktop and workstation memory, plus some entry-level servers. It comes in ECC and non-ECC versions. UDIMMs are generally the lowest capacity per module and, in the used server market, usually the lowest value of the three.
Adds a register that buffers the address and command signals, which lets a server run more modules per channel with stability. This is the workhorse of mainstream rack servers (think Dell PowerEdge, HPE ProLiant, Cisco UCS). RDIMMs are ECC by default and are the most common thing we buy.
Buffers all the signals — address, command, and data — through an on-module buffer, which reduces electrical load and allows the highest capacities per module (128GB, 256GB and up). LRDIMMs live in high-memory servers and often carry the strongest per-module prices.
Most modules carry a sticker with everything you need. Here's what each field tells you:
If you can read one field, make it the part number. The three DRAM makers each use recognizable prefixes, so even the first few characters tell you the generation and type at a glance.
OEM-branded modules (HPE, Dell, Cisco, Lenovo) carry their own part numbers on the sticker, but the DRAM inside is still made by one of these three. If you have the OEM number, that works too — we cross-reference it.
If the label is missing or unreadable, a few physical and code tells separate the generations:
Once you know the type, generation, capacity and part number, you can get an accurate quote. Server RDIMMs and LRDIMMs — especially DDR4 and DDR5 — are where the value is. Here's where to go next:
The fastest way is the part number and the printed label. Registered (RDIMM) and load-reduced (LRDIMM) modules are labeled as such and use buffered part-number families; unbuffered desktop/workstation memory (UDIMM) is not. If you only have the module in hand, RDIMM/LRDIMM are almost always ECC server parts pulled from rack servers, while UDIMMs come from desktops and workstations.
It describes the module's rank and DRAM width. 1R/2R/4R/8R is the number of ranks (1 = single-rank, 2 = dual-rank, and so on). The x4 or x8 is the width of each DRAM chip. It affects capacity and, in the used market, value — so it's worth reading it off the label when you request a quote.
Somewhat. The underlying DRAM maker — Samsung, SK Hynix, or Micron — and the exact part number matter more than an OEM sticker (HPE, Dell, Cisco, Lenovo). Send the part number and we price it on the actual module, not the badge.
Send the part number, a photo of the label, or just a rough count. We'll follow up directly.