dimM

A DIMM, or dual inline memory module, is a type of volatile memory module used in modern computers, including desktops, servers, and workstations. It consists of memory chips mounted on a small printed circuit board with distinct electrical contacts on both edges, plugged into a corresponding dual-inline socket on the motherboard. DIMMs provide a wider data path than older SIMMs, commonly delivering 64-bit data transfer, with additional features for reliability depending on the type.

DIMMs evolve with memory generations, and pin counts vary accordingly. SDR DIMMs used 168 pins, while DDR-based DIMMs use 184 or 240 pins depending on the generation, and DDR4 and DDR5 commonly use 288 pins. Not all generations are physically compatible with every motherboard; the memory type must match the processor, memory controller, and motherboard design.

Common DIMM types include unbuffered (UDIMM) for most desktops and workstations, and registered (RDIMM) or load-reduced (LRDIMM) for servers that require higher memory capacities and improved signal integrity. ECC (error-correcting code) variants, found in many UDIMMs, RDIMMs, and LRDIMMs, can detect and correct single-bit errors, enhancing reliability in critical systems. Parity DIMMs, an older approach, offered error detection but not correction and are less common today. Mixing memory types (for example, ECC with non-ECC or RDIMM with UDIMM) is generally unsupported by most systems.

Form factors include DIMMs for standard desktops and servers, and smaller SO-DIMMs (small outline DIMMs) for laptops, all sharing the same basic principle of a memory module with pins that interface to a motherboard, but differing in size and power/space considerations. Overall, DIMMs are the primary building block of modern volatile memory in many computing platforms.