RDIMM
RDIMM (Registered DIMM) is a memory chip utilized often in servers. It provides better stability and scalability for systems running on a server by putting less of an electrical load on a memory controller. The improved stability and scalability come at a higher price, thus why RDIMMs are found mostly in servers, not desktop or laptop computers.
The main difference between RDIMM and UDIMM (Unbuffered Dual Inline Memory Module), also known as DIMM (Dual In-line Memory Module), memory is that RDIMM is registered memory, and UDIMM is unregistered memory. Registered memory usually performs better than unregistered memory. RDIMM also costs more than UDIMM, another reason computer manufacturers use UDIMM memory in desktop and laptop computers.
The use and compatibility of RDIMM and UDIMM memory is based on the motherboard. In most cases, you cannot (and should not) use RDIMM and UDIMM memory at the same time in a computer. If the motherboard can use registered memory, you should only install RDIMM memory chips for the best performance and compatibility. If the motherboard cannot use registered memory, you can only install UDIMM memory chips.