Historical note: PC RAM modules (SIMMs) in the 80's and 90's commonly had 9 bits per byte. The extra bit was parity, a simple form of error detection. Eventuali

Historical note: PC RAM modules (SIMMs) in the 80's and 90's commonly had 9 bits per byte. The extra bit was parity, a simple form of error detection. Eventuality, as a cost saving measure, some modules faked the parity bit.