Quick answer: for refurbished IBM rack servers, choose the M5 generation (Intel Xeon E5-2600 v3 and DDR4 memory) if you want newer memory and more drive-bay options, and consider the M4 generation (E5-2600 v2 and DDR3) only for light, budget-led jobs. Pick the 2U x3650 for more storage and expansion, or the 1U x3550 to save rack space. "Now Lenovo" simply means Lenovo took over IBM's x86 server business in 2014, so these are the same System x machines. This guide covers what changed between M4 and M5, how to choose, and what to check before you buy.
IBM's System x line was its x86 server range. According to IBM's filing with the US SEC, "On October 1, 2014, IBM and Lenovo completed the initial closing of the sale of IBM's industry standard server business to Lenovo," with the remaining countries expected to follow in early 2015. For you as a buyer this means two things. First, M4 servers were sold under the IBM name and M5 servers under the Lenovo name, which is why you will see both "IBM System x3650 M4" and "Lenovo System x3650 M5" in listings. Second, the technical documentation now lives on Lenovo Press. Lenovo's guides list the x3650 M4 and the x3550 M5 (machine type 5463) as withdrawn products, so refurbished units are the practical route to buy them. If you are also weighing newer Lenovo models, read our Lenovo ThinkSystem model guide and Serverwale's page on refurbished Lenovo servers.
Both are two-socket rack servers. Lenovo's x3550 M5 guide describes a 1U rack-mount server with up to 24 DIMM sockets and up to 12 2.5-inch SAS/SATA hot-swap drive bays. Its x3650 M5 guide describes a 2U server with 8 to 28 small form factor (2.5-inch) drives or up to 14 large form factor (3.5-inch) drives, and support for SAS/SATA hot-swap and NVMe PCIe SSDs. In plain terms, the x3650 gives you more disks and more room, and the x3550 uses half the rack height. If you are short of rack space or unsure how much height you need, see our rack unit sizing guide.
| M4 generation | M5 generation | |
|---|---|---|
| CPU family | Intel Xeon E5-2600 v2 (x3650 M4 guide: up to 12 cores per CPU) | Intel Xeon E5-2600 v3 (x3650 M5 guide: up to 18 cores per CPU); v4 is covered by Lenovo's separate type 8869 guide |
| Memory | DDR3, 24 DIMM sockets, up to 768 GB (x3650 M4 guide) | TruDDR4, 24 DIMM sockets, up to 1.5 TB with 64 GB LRDIMMs (x3650 M5 and x3550 M5 guides) |
| x3650 drive bays | Up to 16 x 2.5-inch, or up to 6 x 3.5-inch (also up to 32 1.8-inch SSD bays) | 8 to 28 x 2.5-inch, or up to 14 x 3.5-inch |
| Power supplies | Up to two redundant hot-swap 550 W, 750 W or 900 W | Up to two redundant hot-swap 550 W, 750 W or 900 W (Platinum) |
| Management | IMM2 | IMM2.1 |
| Practical note | Lower-cost entry; DDR3 is older memory. Fine for light file, print or test workloads | Newer memory and more bays; better fit for virtualization or a longer service life |
The M4 figures come from the x3650 M4 (E5-2600 v2) guide; the x3550 M4 is a 1U sibling, so confirm its exact memory and bay numbers for the unit you are quoted. Maximums depend on the processors fitted and the DIMM type, so a given refurbished server may be configured well below them.
M4 servers use DDR3 and M5 servers use DDR4, and the two are not interchangeable. If you plan to add RAM later, check what is already installed and whether it is registered or load-reduced, because registered and load-reduced DIMMs generally cannot be mixed in one system. Our DDR4 vs DDR5 server RAM guide explains memory generations in general, and Serverwale's DDR3 and DDR4 server RAM price guide covers current upgrade costs.
The x3650 M4 guide lists an integrated ServeRAID M5110e controller supporting RAID 0, 1 and 10. The x3650 M5 guide lists the ServeRAID M5210 and M1215 controllers, which Lenovo describes as supporting RAID 0, 1 and 10, with optional upgrades to RAID 5, 50, 6 and 60. Before buying, ask which controller is fitted and whether it has cache and battery protection. Our RAID levels guide shows which level fits which job, and Serverwale's RAID controller price guide helps if you need to upgrade. Remember that RAID is not a backup.
Both generations use the Integrated Management Module II for remote monitoring and management, and Serverwale says every IBM System x it ships has IMM2 configured for remote power, console and health monitoring. This is useful if the server will sit in a branch office or colocation rack. See our out-of-band management guide for what to set up on day one.
Serverwale's IBM page says refurbished units are priced 60 to 80 percent below new, with delivery in 48 hours in Delhi NCR and 3 to 7 days pan-India, and an itemised GST invoice on every order. It does not publish a price per model, so ask for a written quote. For market context see Serverwale's IBM rack server price guide and the refurbished server price index. If you are comparing brands, read Dell vs HP servers and browse all refurbished servers in India.
Are IBM System x servers the same as Lenovo System x? Yes, they are the same product line. IBM and Lenovo completed the initial closing of the sale of IBM's industry standard server business on 1 October 2014, with remaining countries following in early 2015. Lenovo documentation for the x3550 and x3650 M5 carries the Lenovo name, while M4 servers were sold under the IBM name.
Should I buy an x3650 M4 or an x3650 M5? The M5 uses Intel Xeon E5-2600 v3 processors and DDR4 memory, while the M4 (E5-2600 v2 generation) uses DDR3. If you want newer memory and the larger drive-bay options, the M5 is the more modern choice; the M4 can suit a small, budget-led job. Check the exact configuration of the unit you are quoted.
What is the difference between x3550 and x3650? Per Lenovo's guides, the x3550 M5 is a 1U two-socket rack server with up to 12 2.5-inch drive bays, and the x3650 M5 is a 2U two-socket server with 8 to 28 small form factor bays or up to 14 large form factor drives. The 2U model offers more storage and expansion room; the 1U saves rack space.
Do refurbished IBM servers still get warranty and support in India? Serverwale states a 3-year warranty and 40-point testing on its refurbished IBM rack servers, with on-site engineers for installation, RAID and IMM configuration and AMC in Delhi NCR, Mumbai, Bangalore, Chennai, Hyderabad and Pune. Ask for the warranty terms in writing for your exact unit.
Is IBM no longer making these servers? Lenovo's product guides list the x3650 M4 and the x3550 M5 (type 5463) as withdrawn products. Withdrawn means no longer sold new, so refurbished stock is the main way to buy them. Check parts and support availability for your exact model before a multi-year purchase.
What does IMM2 do on an IBM System x server? IMM2 is the Integrated Management Module II, the built-in management controller used for remote monitoring and management. Serverwale says every IBM System x ships with IMM2 configured for remote power, console and health monitoring.
Tell us the model (x3550 or x3650, M4 or M5), RAM and drive needs, and your city, and we will quote written terms. Serverwale · Phone +91-87962-44410 · WhatsApp https://wa.me/918796244410 · Burari, Delhi 110084, India. See our refurbished IBM rack servers, enterprise solutions, or browse live stock.
Sources: Lenovo Press, x3650 M5 (type 5462), x3550 M5 (type 5463), x3650 M4 (E5-2600 v2); IBM Form 8-K, 2014; Serverwale IBM rack servers page.