Cheapest ECC memory ranked by price per GB

ECC RAM: error-correcting memory for servers, workstations and NAS builds

ECC (error-correcting code) memory stores extra check bits alongside your data, so the memory controller can detect and correct a single flipped bit and report larger errors instead of silently passing on corrupt data. It is standard in servers and workstations and increasingly common in home labs. The 355 ECC modules above are ranked by price per gigabyte, from £1.07/GB to £91.03/GB with a median of £10.58/GB; the cheapest right now is Lafeier 16GB PC3-8500R DDR3 1066Mhz CL7 240Pin ECC REG Memory RAM 1.5V… at £17.11.

ECC UDIMM, RDIMM and LRDIMM

ECC comes in three main module types, and they do not mix: a system takes one type, and putting the wrong one in means no boot.

• ECC UDIMM (unbuffered): a desktop-style module with extra chips for the check bits. Used by entry servers, workstations, and the consumer platforms that support ECC. It is the type for a home server or NAS built on desktop parts.
• RDIMM (registered): adds a register chip that buffers the command and address signals, letting a server run many more modules and much larger capacities. Used by Xeon Scalable, EPYC and most rack and tower servers. RDIMMs do not work in desktop boards.
• LRDIMM (load-reduced): buffers the data lines as well, for the highest capacity per slot. Only worth it when you need very large modules, and it cannot share a system with RDIMMs.

DDR4 RDIMMs have the same notch as DDR4 desktop modules, so they physically fit a desktop slot but will not work there. DDR5 moved the notch, so DDR5 RDIMMs and UDIMMs cannot be swapped by mistake.

Which consumer platforms support ECC UDIMM

• AMD Ryzen: many AM4 and AM5 boards run ECC UDIMMs with the error correction active, some officially and some unofficially. It depends on the board maker and BIOS, so check the board's specification page; the Ryzen PRO APUs support it, and the non-PRO APUs generally do not.
• Intel: consumer chipsets do not enable ECC. You need a workstation chipset such as W680 with a supported Core processor, or a Xeon E or Xeon W system.

One common mistake: DDR5 on-die ECC is not ECC. Every DDR5 chip corrects errors internally, but nothing protects the data on its way to the processor and nothing is reported to the system. For real ECC on DDR5, the module must be sold as an ECC UDIMM or RDIMM.

Home labs, NAS and ZFS

ECC is strongly recommended for TrueNAS and other ZFS storage, because ZFS caches heavily in RAM and checksums data as it is written; a memory error at the wrong moment can be stored to disk with a valid checksum. A Ryzen board with ECC UDIMMs or a used Xeon workstation is the usual route. Plain memory still works, but if the box holds data you care about, ECC is cheap insurance.

Used server RDIMMs are cheap per gigabyte

Data centres retire DDR4 RDIMMs in large numbers, so used 16GB, 32GB and 64GB modules are some of the lowest £/GB memory on the site. If your server or workstation takes RDIMMs, match the speed and rank (for example 2Rx4 or 2Rx8) of the modules already fitted. The server page covers server memory more broadly, and the size pages 16GB and 32GB server RAM narrow the table further.