RAM is a volatile memory that performs tasks to store data that can be quickly accessed, read, and written by the CPU. Double Data Rate (DDR) is a form of Dynamic RAM (DRAM) which is a widely used RAM in server memory technology. It is known for its low-power requirements and high-speed data transfer rate
The memory types are:
Unbuffered low density, low latency Dual In-line Memory Modules (DIMM) which do not include a register or a buffer chip. Generally purchased by customers who have a need for the lowest possible latency, UDIMMs are no longer lower cost than RDIMMs, and often may cost more than RDIMMs due to availability.
Registered DIMMs provide better signal integrity, population of more DIMM channels, and better performance for heavier workloads. They have a slight increase in latency and generally use slightly more power than a UDIMM due to the onboard register.
Load Reduced DIMMs use a buffer to reduce memory loading to a single load on all DDR signals. This allows for greater density. LRDIMMs can navigate outside of these restrictions by using the memory buffer chips. When a server is exclusively configured with LRDIMMs, the memory controllers in the processors automatically shift to serial mode.
A Non-Volatile Dual In-line Memory Module (NVDIMM) is a type of random-access memory that retains its contents, even when electrical power is removed. For example: an unexpected power loss, system crash, or normal shutdown. NVDIMMs improve application performance, data security, and system crash recovery time.