Plan the right DDR5.For your exact server.

RDIMM is registered memory, the default for server platforms up to 64GB per module. LRDIMM is load-reduced, used above 64GB where the buffered electrical load lets you populate more high-capacity DIMMs at full speed. UDIMM is unbuffered, workstation class, only suitable for server use when explicitly listed as ECC UDIMM and the platform's QVL accepts it.

3D-Stacked RDIMM. Multiple DRAM dies stacked vertically inside a single module, giving very high density per stick (128GB and 256GB). Server class, used in memory-dense AI and database workloads.

Multiplexed Rank DIMM. A new DDR5 generation that doubles memory bandwidth by interleaving two ranks per channel. Currently runs at 8800 MT/s, with 12800 MT/s coming. Requires platform support: Intel Granite Rapids and AMD EPYC 9005 today.

Rank is the number of independent sets of memory chips on a module that can be accessed in parallel. 1R is single rank, 2R is dual, 4R is quad, 8R is the very high-capacity 3DS RDIMM tier. Higher rank means more capacity but slightly more strict population rules.

Error-Correcting Code memory detects and corrects single-bit errors on the fly. Server platforms require it. DDR5 also includes on-die ECC for non-ECC UDIMMs, but that is not the same as full ECC for the path between CPU and DIMM. For any server-class workload, order ECC RDIMM or ECC LRDIMM.

How many memory modules sit on one channel. 1DPC means one module per channel, running at the platform's full rated speed. 2DPC means two, which forces a speed downclock on every DDR5 server platform we've shipped. The tool shows the downclock figure on every module card.

The memory controller picks the slowest common denominator. If one DIMM is rated 4800 MT/s and another 5600, the kit clocks to 4800 to keep the slow module within spec. The fix is one speed across the kit. Same logic applies to ranks and capacities.

NUMA is Non-Uniform Memory Access. Each CPU socket owns its own memory; accesses to the other socket's memory cost extra latency. Asymmetric memory population means one socket has less local memory, forcing workloads on that CPU to constantly remote-fetch. Symmetric population removes the asymmetry.

A server vendor's qualified vendor list records memory configurations it has tested for a platform. A QVL entry is useful compatibility evidence, but supported operation still depends on the processor, BIOS, module population and exact part revision. We use current manufacturer documentation and check the intended configuration before you order.

DDR5 JEDEC spec is VDD and VDDQ at 1.1 V, with VPP at 1.8 V. Server modules run JEDEC, not overclocked AMP/XMP profiles. Never mix overclock-profile modules into a server kit; they're rated for workstation use only.