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Memory matched to IBM and Lenovo FRU part numbers. If you have a code like 46W0835, 00YG941 — off a server's parts list, a maintenance record, or an existing module — this is where you find the compatible equivalent.

part numbers across all modules, all DDR4, in registered RDIMM, load-reduced LRDIMM and ECC UDIMM, from 8GB to 128GB, at 2133MHz through 3200MHz. Coverage is the System x and early ThinkSystem era — the generation still running in most datacentres that bought IBM before the Lenovo transition.

IBM's x86 server business became Lenovo in 2014, and the FRU numbering carried across the handover. A part listed under an IBM number and its Lenovo successor are frequently the same module, which is why this page covers both. For current-generation ThinkSystem hardware.

Search by FRU number for an exact match, or send us the list and we'll quote it. Lifetime warranty on every module. Purchase orders, net terms and volume pricing for business, government and education buyers.

How to read a Lenovo or IBM memory part number

Lenovo carries three numbers for every module, and IBM-era System x parts add a fourth. All of them cross-reference to the same NEMIX RAM equivalent, so search this page by whichever one you have.

Format	Example	Where you see it
Option part number — 4X77A, 7X77A, 4ZC7A, 4X70	4X77A08633 · 7X77A01304 · 4ZC7A08709 · 4X70G88334	Lenovo quotes, Lenovo Press product guides, order confirmations. The number a reseller sells the upgrade under. 4X77A = ThinkSystem TruDDR4 / TruDDR5 · 7X77A = first-generation ThinkSystem · 4ZC7A = ThinkSystem entry (ST50, SR250, ST250) and 2933 options · 4X70 = ThinkStation / ThinkPad.
FRU part number — 01DE, 01KR, 01AG, 02JK, 03LB, 47J0	01DE974 · 01KR355 · 47J0253	The module label, XClarity Controller inventory, and Lenovo's parts-lookup site. The number a field technician orders. One option number usually maps to one FRU (7X77A01304 ↔ 01DE974, 46W0672 ↔ 47J0253).
Feature code — 4 characters	AUNC · AUND · B4H4 · B8Y2 · C0U1	Lenovo configurator (DCSC) output and system BOMs. One feature code per memory line; it identifies the option, not a separate part.
IBM System x option / FRU — 46W0, 00D, 95Y, 49Y	46W0672 · 46W0817 · 46W0835 · 00D5044 · 95Y4821	System x M4 and M5 parts lists, IBM quotes, and modules from the pre-2014 era. Lenovo kept these numbers after acquiring System x, so a 46W0 part appears in both IBM and Lenovo documentation for the same module.

If you have a feature code or a configurator BOM and no part number, send us the list and we return the matched set.

TruDDR4, TruDDR5, and the option-vs-FRU trap

TruDDR4 and TruDDR5 are Lenovo's brand names for the memory it qualifies for ThinkSystem — not a different technology. A TruDDR4 2933 RDIMM is a DDR4-2933 RDIMM, and the NEMIX RAM equivalent matches it on the same attributes. The trap is the numbering: the option number on your quote and the FRU number on the label in the server are different strings for the same module, and searching one when the page lists the other returns nothing. Search by the spec on the label (capacity, rank, speed) if the number does not hit.

Memory by generation

Generation	Servers	Platform	Memory
ThinkSystem V4	SR630 V4, SR650 V4, SR650a V4, SR635 V4, SR655 V4, SR645 V4, SR665 V4	Intel Xeon 6 · EPYC 9005	DDR5-6400 TruDDR5 RDIMM · 8 or 12 channels per socket
ThinkSystem V3	SR630 V3, SR650 V3, SR850 V3, SR950 V3, ST650 V3, SD650 V3, SR635 V3, SR655 V3, SR645 V3, SR665 V3, ThinkAgile HX / VX / MX V3	4th / 5th Gen Xeon Scalable · EPYC 9004	DDR5-4800 (DDR5-5600 on 5th Gen Xeon) TruDDR5 RDIMM · 8 (Intel) or 12 (AMD) channels · no LRDIMM
ThinkSystem V2	SR630 V2, SR650 V2, SR850 V2, SR860 V2, ST650 V2, SD630 V2, ThinkAgile HX / VX V2	3rd Gen Xeon Scalable	DDR4-3200 TruDDR4 RDIMM · 8 channels per socket · 3DS RDIMM at 128GB and 256GB
ThinkSystem AMD (1st gen)	SR635, SR655, SR645, SR665	EPYC 7002 / 7003	DDR4-3200 TruDDR4 RDIMM · 8 channels per socket
ThinkSystem (1st gen Intel)	SR530, SR550, SR570, SR590, SR630, SR650, SR850, SR860, SR950, ST550, SD530, SN550, SN850, ThinkAgile HX / VX	1st / 2nd Gen Xeon Scalable	DDR4-2666 or DDR4-2933 TruDDR4 RDIMM or LRDIMM · 6 channels per socket · 2933 requires 2nd Gen Xeon
System x M5 / X6	x3550 M5, x3650 M5, x3850 X6, x3950 X6, nx360 M5, Flex x240 M5	Xeon E5-2600 v3 / v4 · E7 v3 / v4	DDR4-2133 or DDR4-2400 RDIMM or LRDIMM · 4 channels per socket · 2400 requires v4
System x M4	x3550 M4, x3650 M4, x3500 M4, x3750 M4, Flex x240	Xeon E5-2600 / v2	DDR3-1333 / 1600 / 1866 RDIMM or LRDIMM · 4 channels per socket
Entry ThinkSystem	ST50 V3, ST250 V3, SR250 V3 · ST50 V2, ST250 V2, SR250 V2 · ST50, ST250, SR250, SR150	Xeon E-2400 · E-2300 · E-2100 / E-2200	DDR5-4800 ECC UDIMM (V3) · DDR4-3200 ECC UDIMM (V2) · DDR4-2666 ECC UDIMM (1st gen) · ST50 also takes non-ECC UDIMM · unbuffered only
ThinkEdge	SE350, SE350 V2, SE360 V2, SE450, SE455 V3	Xeon D · Xeon Scalable · EPYC 8004	DDR4 ECC SODIMM (SE350) · DDR4-3200 RDIMM (SE450, SE360 V2) · DDR5-4800 RDIMM (SE455 V3) — confirm per model

Generation lists are representative. The FRU number on the installed module, or the option number on your original order, is the authority. This page carries the DDR4 System x and ThinkSystem range; current DDR5 ThinkSystem V3 and V4 parts are listed under their own Lenovo part numbers — search the option number or send us the model.

How to find what is installed without downtime

XClarity Controller (ThinkSystem): Inventory → Memory. Every slot is listed with capacity, speed, rank, manufacturer, and the Lenovo FRU number. The same page shows the operating speed after POST.
IMM2 (System x M4 / M5): Server Management → Server Properties → Hardware → Memory gives the same per-DIMM detail on the IBM-era platforms.
OneCLI or XClarity Administrator: onecli inventory getinfor --ftype memory on a single node, or an XClarity Administrator inventory export across the whole estate — the starting point for a multi-node quote.
Lenovo Press product guide for the model lists every qualified option number with its capacity, rank, and speed, and states the population rules for that server.

Population rules that decide whether it posts

One module type per server. RDIMM, LRDIMM, and 3DS RDIMM cannot be mixed in a ThinkSystem or System x; entry servers take UDIMM only. If the server is populated with RDIMM, add RDIMM.
Follow the Lenovo population order. ThinkSystem Setup Guides give an explicit slot order per processor for Independent mode (one DIMM per channel first) and a separate table for Mirroring. A lone 64GB module in a 6-channel SR650 socket runs at one-sixth of available bandwidth.
Balance across processors. Lenovo UEFI expects symmetric population between CPUs; an unbalanced layout is logged in XCC and leaves one processor without local memory.
Match capacity, speed, and rank within a channel. Mixed speeds run at the slowest module; mixed ranks in a channel can force a lower speed or block Mirroring. Identical modules across the server are the safe configuration, which is why we sell matched kits sized to the channel count.
Two DIMMs per channel may cost speed. DDR4-2933 can step to 2666 at 2DPC on first-generation ThinkSystem depending on the processor; DDR4-3200 steps to 2933 on some V2 layouts; DDR5-4800 steps to 4400 on V3. XCC shows the resulting speed.
The CPU sets the ceiling. An SR650 with a Xeon Silver 4110 runs 2933 modules at 2400. Check the processor's rated memory speed before paying for the faster grade.
Memory modes need symmetric layout. Independent is the default. Mirroring halves usable capacity and requires identical pairs in the mirrored channels; check the Setup Guide before enabling on a partial upgrade.

What "compatible equivalent" means here — and what XCC will say

A NEMIX RAM module listed against a Lenovo or IBM part number matches it on every attribute the memory controller checks: DDR generation, capacity, ECC, buffering (registered, load-reduced, or unbuffered), rated speed, rank organization, voltage, and pin count. It is built on DRAM from the same manufacturers Lenovo sources for TruDDR4 and TruDDR5 and tested in a ThinkSystem or System x of the target generation before listing. XClarity Controller may log an informational event noting a non-Lenovo DIMM in inventory; the server boots, recognizes full capacity, and runs the modules at spec with no performance penalty. Mixing NEMIX RAM with Lenovo-branded modules of the same spec in one server is supported. Every module carries a lifetime replacement warranty with free US-based technical support.

Ordering for fleets

NEMIX RAM is a registered federal supplier (UEI GV8MMYNDJ5J1, CAGE 59AB2) and accepts purchase orders with net terms for business, government, and education buyers. For multi-node, ThinkAgile cluster, or Flex chassis upgrades, send the Lenovo quote, the option or feature-code list with node count, or an XClarity Administrator inventory export, and we return the full set matched and shipped together. Volume and reseller pricing is available on request.

Frequently asked

Does Lenovo support the server with third-party memory? The server warranty and support contract remain in force. Lenovo may decline to troubleshoot issues it attributes to non-Lenovo DIMMs; our lifetime warranty and support cover the modules.

My IBM part number is not on this page. IBM issued several option numbers for the same spec across DRAM vendors, and Lenovo added FRUs on top. Filter by capacity, rank, and speed from the label, or send us the number and we will match it.

Is TruDDR4 required? TruDDR4 is Lenovo's label for memory it has qualified; the server checks generation, capacity, type, speed, and rank, not the label. The equivalent on this page meets the same specification.

x3650 M5 — 2133 or 2400? Both fit; 2400 runs at full speed only with an E5-2600 v4 processor. With a v3, buy 2133 and save the difference.

Does ThinkSystem V3 or V4 take LRDIMM? No. DDR5 generations are RDIMM-only; high capacities use 128GB and 256GB RDIMMs.