"registered" memory

[o770]

what is a "registered" memory? what the differences to a not registered?
thanks.

[Violator]

Registered RAM is ECC RAM :

Error correction code (ECC) RAM not only checks for errors but can even correct some of them along the way. ECC RAM is more expensive than other types of RAM, and it's typically found only in machines, such as file servers, that are used for mission-critical applications. ECC and non-ECC RAM cannot be mixed. It is slower than non-ECC RAM.

[Intraveinous]

I always thought ECC stood for 'Error Checking and Correction', but if I'm wrong, lemme know... I am an acronym junkee... :D
Peace
John