Modern desktop processors operate with a 64-bits bus. However, some SDRAM DIMMs are 72-bit wide, why? Additional 8-bit are called “parity bits”, or "parity byte". The parity bits offer the computer the possibility for error detection and correction. In order to realize this useful feature during the write procedure, for each byte of the bus (64 bits = 8 x 8 bits, i.e. the bus is 8 bytes wide) the so called checksum is build and stored in a single parity bit. Thus, for a 64-bit wide bus 8-parity-bits are needed.