Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a central processing unit|processor. Memory bandwidth is usually expressed in units of bytes per second|bytes/second, though this can vary for systems with natural data sizes that are not a multiple of the commonly used 8-bit bytes.
Memory bandwidth that is advertised for a given memory or system is usually the maximum theoretical bandwidth. In practice the observed memory bandwidth will be less than (and is guaranteed not to exceed) the advertised bandwidth. A variety of computer benchmarks exist to measure sustained memory bandwidth using a variety of access patterns. These are intended to provide insight into the memory bandwidth that a system should sustain on various classes of real applications.