(Symmetric MultiProcessing) An architecture in which two or more processing units share the same memory. SMP dates back to the 1960s when IBM offered a System/360 dual-CPU model. Digital Equipment followed, and companies such as Sequent, Pyramid and Encore specialized in SMP on Unix platforms. Early SMP systems contained multiple single-core CPUs, which evolved into today's chips with multiple cores that are used in every computing device from servers to smartphones (see multicore). All major operating systems support SMP. See Sequent, Encore and Fujitsu Siemens. A Pool of Resources Whether multiple single-core CPUs or one CPU with multiple cores, one of the CPUs/cores boots the system and loads the SMP operating system. There is only one instance of the operating system, and it uses the CPUs or cores as a pool of processing resources that execute simultaneously. However, unless clusters of two or more independent SMP systems are used, if one CPU or core fails, the system typically goes down. See high availability. Whatever Can Be Overlapped SMP speeds up the processes that can be overlapped such as running multiple applications simultaneously. If an application is multithreaded, which allows for concurrent operations within the application itself, then SMP can improve the performance of that single application. Contrast with MPP. See NUMA.