ECC RAM

From Extreme Overclocking

ECC RAM (Error Correcting Code RAM) is a type of RAM typically used in environments were high reliability and no data corruption is needed, such as workstations and servers. However ECC RAM typically operates slower than its non-ECC counterparts. For example if one was to test a stick of DDR RAM at 200mhz, 2-2-2-5 timings, and a similarly sized stick of ECC DDR RAM at 200mhz, 2-2-2-5 mhz, the unregistered (another name for non-ECC) RAM would win in bandwidth and performance.

Credits: sdat1333