It is a memory module with registers between the DRAM module and the system memory controller. This reduces the electrical load on the memory controller, making a single system using multiple memory modules more stable. In contrast to registered memory, traditional memory is often referred to as unbuffered memory or unregistered memory. When manufactured as dual inline memory modules (DIMMs), registered memory modules are called RDIMMs and unregistered memory are called UDIMMs.
Registered memory is generally more expensive because it is sold less and requires additional circuitry, so it is generally only used in applications where scalability and robustness needs outweigh price requirements, so register memory is often used in servers.
Although most register memory is equipped with error correction (ECC), there is no relationship between register memory and ECC, and the two can exist alone or together. For example, some unregistered ECC memory is used on workstation or entry-level server motherboards.