UDIMM – Unbuffered Dual Inline Memory Module. This is a DIMM (Dual Inline Memory Module) card containing DRAM (Dynamic Random Access Memory) with no signal buffering, meaning that address and control signals directly reach the DRAM chip on the Host (PC or server) DIMM without first passing through a buffer and without any timing adjustment. The UDIMM provides parallel data transfer and is built to ensure that the transmission distance between the CPU and each DRAM chip is equal. In general UDIMMS are simpler and slightly more affordable to manufacture than buffered DIMMs. They can have a lower access latency. UDIMMs cannot support full server RAM allocation (maximum capacity) as that requires buffering.
Alternative RDIMMs (Registered DIMMs) include a register, or buffer, between the memory controller and the memory chips to help stabilize and manage the electrical load of the memory modules. It enables RDIMMs to support larger memory capacities than is possible with UDIMMs. RDIMMs are mostly found in workstations and servers as they provide better reliability and stability.
