Unbuffered memory

Unbuffered memory (or unregistered memory) is RAM where there is no hardware register between the memory controller and the RAM chips. Unbuffered memory is the opposite of registered memory. Registered memory is more stable, one clock cycle slower, and more expensive than unbuffered memory. Registered memory is usually used in servers and workstations, while normal PCs usually use unbuffered memory.

Some high-end hardware, such as servers, require the use of registered memory.

In the past, registered memory was called buffered memory and unregistered memory was called unbuffered memory. Registered memory got renamed in common use, but unbuffered memory did not.

Buffered (Registered) Memory has ECC (Error Code Correction) thus making it more reliable and also a bit slower than unregistered memory. ECC finds and corrects any errors while reading and writing to the memory. This is why you want to use buffered ram in servers, to help prevent glitches and blue screens.