Lenovo ThinkSystem servers run everywhere from a single ST50 in a back office to racks of SR650s and liquid-cooled SD650 supercomputing nodes. Across four generations and two processor families, the right memory changes with every model and generation, and an SR650, an SR650 V2 and an SR650 V3 each take a different module. NEMIX RAM has now completed its Lenovo server catalog: 69 server listings covering every ThinkSystem and ThinkEdge generation from the first SR630 to the Xeon 6 V4 systems, plus 126 listings matched to Lenovo server memory option part numbers. Every server listing states the slot count and the maximum memory Lenovo specifies for that model. This guide explains how to read a ThinkSystem model name, which memory each generation takes, and how much each server holds.
In this guide: Reading a ThinkSystem model · Memory by generation · V4 and Xeon 6 · V3: Intel and AMD · DDR4 generations · Entry servers · Every server: slots and maximum · Part numbers · Population rules · FAQ
Reading a ThinkSystem model name
A ThinkSystem model such as SR665 V3 tells you three things that decide the memory:
- The letters are the family: SR for rack servers, ST for towers, SD for dense multi-node servers, SC for the SC750 V4 supercomputing node, SN for Flex System compute nodes, and SE for ThinkEdge edge servers.
- The last digit is the processor maker. Across the servers we list, models ending in 5 run AMD EPYC (SR635, SR645, SR655, SR665, SR675, SR685a, SD535, SD665, SE455, ST45 V3) and models ending in 0 run Intel Xeon.
- The V number is the generation. No suffix is the first generation, then V2, V3 and V4. The generation, more than anything else, decides whether the server takes DDR4 or DDR5 and at what speed.
The model is on the front bezel or the pull-out information tab, and the four-character machine type (for example 7Z73) is on the system label and in Lenovo XClarity. Type the model into the search bar at the top of the page, generation included, and the matching listing comes up.
Which memory does my ThinkSystem server take?
ThinkSystem memory follows the generation and the processor. Every server below takes registered ECC memory (RDIMM) except the entry towers and single-socket rack servers, which take unbuffered ECC UDIMMs. DDR4 and DDR5 modules are keyed differently and will not fit each other's slots.
| Generation | Processors | Memory | Examples |
|---|---|---|---|
| V4 | Intel Xeon 6 | DDR5-6400 RDIMM (5200 MT/s with two DIMMs per channel) | SR630 V4, SR650/SR650a V4, SR850 V4, SR860 V4, SC750 V4 |
| V3 | 4th and 5th Gen Intel Xeon Scalable | DDR5-4800 or DDR5-5600 RDIMM, depending on the processor | SR630 V3, SR650 V3, ST650 V3, SD530 V3, SR860 V3/SR850 V3 |
| V3 | AMD EPYC 9004 and 9005 | DDR5 RDIMM: 6400 MT/s with EPYC 9005, 4800 MT/s with EPYC 9004 | SR635 V3, SR645 V3, SR665 V3, SR675 V3, SD665 V3/SD665-N V3 |
| V2 | 3rd Gen Intel Xeon Scalable | DDR4-3200 RDIMM | SR630 V2, SR650 V2, ST650 V2, SR850 V2, SD630 V2 |
| First generation | AMD EPYC 7002 and 7003 | DDR4-3200 RDIMM (2933 MT/s with two DIMMs per channel) | SR635, SR645, SR655, SR665 |
| First generation | 1st and 2nd Gen Intel Xeon Scalable | DDR4-2933 RDIMM (2666 MT/s with 1st Gen processors) | SR630, SR650, SR550, SR950, SD530 |
| Entry, all generations | Intel Xeon E and AMD EPYC 4004 | ECC unbuffered UDIMM: DDR5 on V3, DDR4 on V2 and earlier | ST50 V2, ST250 V2, SR250 V2, ST45 V3 |
V4: Xeon 6 and DDR5-6400
The V4 generation (SR630 V4, SR650/SR650a V4, SR680a V4, SR850 V4, SR860 V4, SC750 V4) runs Intel Xeon 6 processors and takes DDR5-6400 RDIMMs, the fastest standard registered memory Lenovo supports. With one DIMM per channel the modules run at 6400 MT/s; filling the second slot in each channel raises capacity and drops the speed to 5200 MT/s. The two-socket SR630 V4 and SR650 V4 hold 32 modules and up to 8TB; the four-socket SR850 V4 and SR860 V4 hold 64 modules and up to 16TB.
V3: the processor decides the speed
V3 is where Intel and AMD part ways. The two-socket Intel V3 servers (SR630 V3, SR650 V3, ST650 V3, SD530 V3) take DDR5 at 4800 MT/s with 4th Gen Xeon Scalable and 5600 MT/s with 5th Gen; NEMIX RAM lists them at DDR5-5600, which also runs at 4800 in a 4th Gen system. The four-socket SR850 V3 and SR860 V3 and the eight-socket SR950 V3 run 4th Gen Xeon Scalable, so their memory runs at 4800 MT/s: the SR950 V3 listing is DDR5-4800, and the DDR5-5600 modules on the SR860 V3/SR850 V3 listing run at 4800 in those servers.
The AMD V3 servers (SR635 V3, SR645 V3, SR665 V3, SR675 V3, SD535 V3, SD665 V3/SD665-N V3) run EPYC 9004 or EPYC 9005 across 12 memory channels per processor. EPYC 9005 runs DDR5 at up to 6400 MT/s and EPYC 9004 at up to 4800 MT/s. These listings are DDR5-6400, which covers both: in an EPYC 9004 server the modules run at 4800, and the same modules run at 6400 if the processors are later upgraded. If you are adding to installed DDR5-4800 modules, match their capacity and rank and the whole set runs at 4800.
DDR4 generations still in service
The V2 Intel servers run 3rd Gen Xeon Scalable and take DDR4-3200 RDIMMs: the two-socket SR630 V2, SR650 V2, ST650 V2 with 8 channels per processor, and the four-socket SR850 V2, SR860 V2 with 6. The first-generation Intel servers (SR630, SR650, SR530, SR550, SR590, SR950) run 1st and 2nd Gen Xeon Scalable with 6 channels per processor and take DDR4-2933, which runs at 2666 MT/s with 1st Gen processors. The first-generation AMD servers (SR635, SR645, SR655, SR665) run EPYC 7002 and 7003 and take DDR4-3200. Each DDR4 listing offers module sizes from 16GB up to 64GB or 128GB, depending on what Lenovo supports for the model; match what is installed, since modules of different ranks and sizes should not be mixed within a channel group.
Entry towers and single-socket rack servers
The ST50, ST250, SR250 and ST45 families are based on Intel Xeon E or AMD EPYC 4004 processors and take unbuffered ECC memory (ECC UDIMM), not the registered RDIMMs of the larger servers. The V2 and first-generation models (ST50 V2, ST250 V2, SR250 V2, ST50, ST250, SR250) take DDR4-3200 ECC UDIMMs; the V3 models take DDR5 ECC UDIMMs. Most have 4 slots and a 128GB maximum; the ST45 V3 has 2 slots and holds 64GB. An RDIMM will not work in these servers, and a UDIMM will not work in a registered-memory server.
Every Lenovo server we list: slots and maximum memory
The maximum is the platform maximum Lenovo specifies for the full server with every slot filled at the largest supported module size; dense and multi-node servers are listed per node. Each listing offers single modules and matched kits sized to the server's memory channels.
Rack servers
| Server | Memory | Slots | Maximum |
|---|---|---|---|
| SR630 V4 | DDR5-6400 RDIMM | 32 | 8TB |
| SR650/SR650a V4 | DDR5-6400 RDIMM | 32 | 8TB |
| SR680a V4 | DDR5-6400 RDIMM | 32 | 4TB |
| HS350X V3 | DDR5-4800 RDIMM | 16 | 1TB |
| SR250 V3/ST250 V3 | DDR5-4800 ECC UDIMM | 4 | 128GB |
| SR630 V3 | DDR5-5600 RDIMM | 32 | 4TB |
| SR635 V3 | DDR5-6400 RDIMM | 12 | 3TB |
| SR645 V3 | DDR5-6400 RDIMM | 24 | 6TB |
| SR650 V3 | DDR5-5600 RDIMM | 32 | 4TB |
| SR655 V3 | DDR5-5600 RDIMM | 12 | 1.5TB |
| SR665 V3 | DDR5-6400 RDIMM | 24 | 6TB |
| SR675 V3 | DDR5-6400 RDIMM | 24 | 3TB |
| SR680a V3 | DDR5-5600 RDIMM | 32 | 4TB |
| SR685a V3 | DDR5-5600 RDIMM | 24 | 3TB |
| SR780a V3 | DDR5-5600 RDIMM | 32 | 4TB |
| SR250 V2 | DDR4-3200 ECC UDIMM | 4 | 128GB |
| SR630 V2 | DDR4-3200 RDIMM | 32 | 8TB |
| SR650 V2 | DDR4-3200 RDIMM | 32 | 8TB |
| SR670 V2 | DDR4-3200 RDIMM | 32 | 2TB |
| SR250 | DDR4-3200 ECC UDIMM | 4 | 128GB |
| SR530 | DDR4-2933 RDIMM | 12 | 768GB |
| SR550 | DDR4-2933 RDIMM | 12 | 768GB |
| SR570 | DDR4-2933 RDIMM | 16 | 1TB |
| SR590 | DDR4-2933 RDIMM | 16 | 1TB |
| SR630 | DDR4-2933 RDIMM | 24 | 3TB |
| SR635 | DDR4-3200 RDIMM | 16 | 2TB |
| SR645 | DDR4-3200 RDIMM | 32 | 8TB |
| SR650 | DDR4-2933 RDIMM | 24 | 3TB |
| SR655 | DDR4-3200 RDIMM | 16 | 2TB |
| SR665 | DDR4-3200 RDIMM | 32 | 8TB |
| SR670 | DDR4-2933 RDIMM | 24 | 1.5TB |
Tower servers
| Server | Memory | Slots | Maximum |
|---|---|---|---|
| ST250 V3 | DDR5-4800 ECC UDIMM or DDR5-5600 ECC UDIMM | 4 | 128GB |
| ST45 V3 | DDR5-5600 ECC UDIMM | 2 | 64GB |
| ST50 V3 | DDR5-4800 ECC UDIMM or DDR5-5600 ECC UDIMM | 4 | 128GB |
| ST650 V3 | DDR5-5600 RDIMM | 32 | 4TB |
| ST250 V2 | DDR4-3200 ECC UDIMM | 4 | 128GB |
| ST50 V2 | DDR4-3200 ECC UDIMM | 4 | 128GB |
| ST650 V2 | DDR4-3200 RDIMM | 32 | 4TB |
| ST250 | DDR4-3200 ECC UDIMM | 4 | 128GB |
| ST50 | DDR4-3200 ECC UDIMM | 4 | 64GB |
| ST550 | DDR4-2933 RDIMM | 12 | 768GB |
Mission-critical servers
| Server | Memory | Slots | Maximum |
|---|---|---|---|
| SR850 V4 | DDR5-6400 RDIMM | 64 | 16TB |
| SR860 V4 | DDR5-6400 RDIMM | 64 | 16TB |
| SR860 V3/SR850 V3 | DDR5-5600 RDIMM | 64 | 16TB |
| SR950 V3 | DDR5-4800 RDIMM | 128 | 32TB |
| SR850 V2 | DDR4-3200 RDIMM | 48 | 12TB |
| SR860 V2 | DDR4-3200 RDIMM | 48 | 12TB |
| SR850 | DDR4-2933 RDIMM | 48 | 6TB |
| SR860 | DDR4-2933 RDIMM | 48 | 6TB |
| SR950 | DDR4-2933 RDIMM | 96 | 12TB |
All mission-critical servers listings.
Dense, HPC and Flex nodes
| Server | Memory | Slots | Maximum |
|---|---|---|---|
| SC750 V4 | DDR5-6400 RDIMM | 24 | 3TB |
| SD530 V3 | DDR5-5600 RDIMM | 16 | 2TB |
| SD535 V3 | DDR5-6400 RDIMM | 12 | 1.5TB |
| SD550 V3 | DDR5-5600 RDIMM | 16 | 2TB |
| SD650 V3/SD650-N V3/SD650-I V3 | DDR5-5600 RDIMM | 16 | 2TB |
| SD665 V3/SD665-N V3 | DDR5-6400 RDIMM | 24 | 3TB |
| SD630 V2 | DDR4-3200 RDIMM | 16 | 2TB |
| SD650 V2/SD650-N V2 | DDR4-3200 RDIMM | 16 | 2TB |
| SN550 V2 | DDR4-3200 RDIMM | 16 | 2TB |
| SD530 | DDR4-2933 RDIMM | 16 | 2TB |
| SD650 | DDR4-2933 RDIMM | 12 | 1.5TB |
| SN550 | DDR4-2933 RDIMM | 24 | 3TB |
| SN850 | DDR4-2933 RDIMM | 48 | 6TB |
All dense, hpc and flex nodes listings.
ThinkEdge edge servers
| Server | Memory | Slots | Maximum |
|---|---|---|---|
| SE455 V3 | DDR5-5600 RDIMM | 6 | 768GB |
| SE455i V3 | DDR5-5600 RDIMM | 6 | 768GB |
| SE360 V2/SE350 V2 | DDR4-3200 RDIMM | 4 | 256GB |
| SE350 | DDR4-3200 RDIMM | 4 | 128GB |
| SE450 | DDR4-3200 RDIMM | 8 | 1TB |
All thinkedge edge servers listings.
Ordering by Lenovo part number
Lenovo sells server memory under option part numbers such as 4X77A94004 or 4ZC7A08699. If you are adding to modules already installed, or ordering from a Lenovo quote, search the part number: NEMIX RAM has 126 listings matched to Lenovo server memory options, each to the density, rank and speed of the original module. They are in the Lenovo ThinkSystem and ThinkEdge collection alongside the server listings, and with older IBM and Lenovo FRU numbers in Lenovo and IBM part-number memory.
Beyond servers: ThinkStation, ThinkPad and ThinkCentre
The same catalog work covers Lenovo workstations and PCs: 15 ThinkStation workstation listings, from SODIMMs in the P3 Ultra and P3 Tiny to registered RDIMMs in the P5, P7, P8 and PX, and 80 ThinkPad, ThinkBook, ThinkCentre, IdeaPad, Legion and LOQ listings for laptops and desktops with replaceable memory. The Lenovo memory guide page maps every Lenovo family to its collection.
Population rules for ThinkSystem servers
- Fill every channel evenly. Memory bandwidth scales with populated channels: 6 per processor on 1st and 2nd Gen Xeon Scalable and the four-socket SR850 V2 and SR860 V2, 8 on the other 3rd Gen and all 4th and 5th Gen Xeon Scalable, Xeon 6 6700 and EPYC 7002/7003 systems, and 12 on EPYC 9004/9005 and the 12-channel Xeon 6 systems. That is why kit sizes differ between listings, from kits of 6 and 12 to kits of 8 and 16.
- Use one module size and type per server. Identical capacity, rank and speed across all slots gives the best speed and stability.
- One DIMM per channel is fastest. On servers with two slots per channel, the second DIMM raises capacity but can lower the memory speed.
- Dense and Flex nodes are populated per node. Each SD or SN node has its own slots and needs its own set of modules.
Frequently asked questions
Will DDR5 memory work in my ThinkSystem V2 server?
No. V2 and first-generation ThinkSystem servers take DDR4; V3 and V4 servers take DDR5. The modules are physically different and will not fit each other's slots.
My SR665 V3 has EPYC 9004 processors. Should I buy DDR5-4800 or DDR5-6400?
Either runs at 4800 MT/s with EPYC 9004. The NEMIX RAM listing is DDR5-6400, which runs at 4800 now and at 6400 if the server is later upgraded to EPYC 9005 processors.
Does my ThinkSystem server take RDIMM or UDIMM?
The rack, mission-critical, dense and edge servers and the ST550 and ST650 towers take registered RDIMMs. The ST50, ST250, SR250 and ST45 families take unbuffered ECC UDIMMs. Each listing names the type.
Can I add NEMIX RAM modules to the Lenovo memory already installed?
Yes, if the new modules match the installed ones in type, capacity, rank and speed. Keep the population identical within each processor's channels; when in doubt, send us the Lenovo part number printed on an installed module.
How much memory does my ThinkSystem server hold?
Each server listing states the slot count and the maximum Lenovo specifies, and the tables above list both for every server we cover: from 64GB on the ST50 to 32TB on the eight-socket SR950 V3.
Do you supply memory for a Lenovo server refresh or a whole fleet?
Yes. Purchase orders, net terms and volume pricing are available for data centers, HPC sites, universities, government buyers and resellers. Send us the models or machine types and the target capacity and we will quote the matching modules.
Buying Lenovo server memory from NEMIX RAM
NEMIX RAM is a US-based server memory specialist, in business since 1993. Every module is researched, matched, and compatibility-tested by NEMIX RAM, is JEDEC-compliant, and is backed by a lifetime warranty. Purchase orders, net terms and volume pricing are available for data centers, HPC sites, universities, government buyers and resellers. Request a quote for a rack refresh or a spares pool, or send us your Lenovo machine type and we will confirm the right module before you order.
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