Multicore computing

A multicore processor is a processor that includes multiple execution units ("cores"). These processors differ from superscalar processors, which can issue multiple instructions per cycle from one instruction stream (thread); by contrast, a multicore processor can issue multiple instructions per cycle from multiple instruction streams. Each core in a multicore processor can potentially be superscalar as well—that is, on every cycle, each core can issue multiple instructions from one instruction stream.

Simultaneous multithreading (of which Intel's HyperThreading is the best known) was an early form of pseudo-multicoreism. A processor capable of simultaneous multithreading has only one execution unit ("core"), but when that execution unit is idling (such as during a cache miss), it uses that execution unit to process a second thread. Intel's Core and Core 2 processor families are Intel's first true multicore architectures. IBM's Cell microprocessor, designed for use in the Sony Playstation 3, is another prominent multicore processor.