LRDIMM (Load-Reduced DIMM) adds a memory buffer chip that isolates the data lines from the memory controller, on top of the command/address buffering a plain RDIMM already does - which is what lets LRDIMM support more ranks per channel and higher total capacity than RDIMM on the same platform. It is its own module class: Kingston's own documentation groups it with UDIMM, RDIMM and MRDIMM under one rule - "Cannot be mixed in the same system. If mixed, the server may not boot."
Updated ยท vendor documents read 14-16 September 2026
This page narrows to LRDIMM specifically. For the full six-class picture - UDIMM, ECC UDIMM, RDIMM, 3DS RDIMM, LRDIMM and MRDIMM together - see our module classes overview.
A plain RDIMM buffers the command and address signals through a register chip, which reduces electrical load on the memory controller and lets more ranks share a channel than an unbuffered UDIMM can. LRDIMM goes one step further: its memory buffer chip also isolates the data lines, not just command/address. That additional isolation is the entire mechanism - it is what allows a channel populated with LRDIMM to carry more ranks and reach a higher total capacity than the same channel populated with plain RDIMM, holding the platform constant.
These are easy to conflate because both show up at the top of a server's capacity range, but they solve different problems and Intel's own memory population rules treat them as separate named types. 3DS (3D-stacked, TSV) RDIMM stacks multiple DRAM die within a single package to raise the capacity any one chip can hold - it is a packaging answer to a per-chip capacity ceiling. LRDIMM's buffer chip instead raises how many ranks a channel can carry - it is a signal-integrity answer to a per-channel rank ceiling. The two techniques can combine: Intel names "3DS LRDIMM" explicitly as its own fourth type in the same sentence as plain RDIMM, LRDIMM and 3DS RDIMM, confirming the site does not treat it as a variant of either parent class.
Intel's own server board documentation states the shared failure mode for all four: "Mixing of DDR4 DIMM types (RDIMM, LRDIMM, 3DS RDIMM, 3DS LRDIMM) within or across processor sockets produces a Fatal Error Halt during memory initialization." A sibling board family's documentation states an almost identical rule in its own words.
Lenovo Press's own ThinkSystem memory-summary ordering tables give a concrete, dated example of how high-capacity 3DS modules are actually labelled: "ThinkSystem 256GB TruDDR5 6400MHz (4Rx4) 3DS RDIMM" and "(8Rx4) 3DS RDIMM" both appear as real, currently-listed shipping parts. See our ranks-explained page for what the 4Rx4/8Rx4 notation itself means.
Even within a single correctly-matched module class, capacity and organization still have to agree. Dell's own PowerEdge R660 documentation states it directly: "Mixing different capacities, x4 with x8 DRAM, or 3DS with non-3DS RDIMMs is not supported." That is a narrower rule than the class-mixing rule above - it applies inside one class, not across classes - and it is exactly the kind of cell our mixing-rules matrix exists to state with its own citation rather than leave implied.
Whether your platform requires LRDIMM at a given capacity - and which capacities that threshold sits at - is set by the OEM, not by this page. See our OEM-verified platform pages for the exact per-DIMM ceilings we have checked directly, or the manufacturer's own supported-memory list for anything we have not yet built.
Cheapest in-stock LRDIMM modules right now, computed live rather than quoted from a snapshot.
| Brand | Module | Capacity | Gen | $/GB | |
|---|---|---|---|---|---|
| Supermicro | B07DFLTWN3 | 64GB | DDR4 | $6.23 | Buy Now |
LRDIMM adds a memory buffer chip that isolates the data lines from the memory controller, not just the command/address lines that a plain RDIMM's register chip buffers. That extra isolation is what lets LRDIMM support more ranks per channel and reach higher total capacity than RDIMM on the same platform, without our making any claim about speed.
No, and Intel's own documentation treats them as separate types. 3DS RDIMM stacks multiple DRAM die within one package to raise capacity per chip; LRDIMM adds a data-line buffer to raise rank count per channel. A module can combine both (3DS LRDIMM), which Intel's memory population rules name as its own fourth type alongside plain RDIMM, LRDIMM and 3DS RDIMM.
No. Kingston's own documentation groups LRDIMM with UDIMM, RDIMM and MRDIMM under a single rule: "Cannot be mixed in the same system. If mixed, the server may not boot." Intel's server board memory population rules describe the DDR4 failure mode for exactly this combination as a "Fatal Error Halt during memory initialization."
Capacity and rank count, not speed. A platform's own supported-memory documentation states which capacities require LRDIMM (or 3DS LRDIMM) to reach - it is a threshold the OEM sets, not a preference the buyer expresses. See our OEM-verified platform pages for exact per-DIMM ceilings by model.
It can - and this is a separate rule from the module-class question above. Dell's own PowerEdge R660 documentation states: "Mixing different capacities, x4 with x8 DRAM, or 3DS with non-3DS RDIMMs is not supported." That combination rule sits inside a single module class; see our population-rules page for the fuller picture.
Read the module's own printed label or the listing's stated specification first. Where our own catalogue carries a listing whose class could not be confirmed against the named manufacturer's own datasheet, we label it unverified rather than guess - see our module-classes page for a worked example of exactly that happening with three of our own highest-capacity rows.
Specification claims on this page were checked against the pages below on 16 September 2026. Where a widely-repeated figure did not survive that check, we report what the source says now and say so in the text rather than repeating the familiar number.