A full system simulator provides virtual hardware that is independent of the nature of the host computer.
The full-system model typically includes processor cores, peripheral devices, memories, interconnection buses, and network connections.
The use of multi-core processors is driving the need for full system simulation, because it can be extremely difficult and time-consuming to recreate and debug errors without the controlled environment provided by virtual hardware.
Often, a cycle-accurate simulator is used when designing new microprocessors – they can be tested, and benchmarked accurately (including running full operating system, or compilers) without actually building a physical chip, and easily change design many times to meet expected plan.
Cycle-accurate simulators must ensure that all operations are executed in the proper virtual (or real if it is possible) time – branch prediction, cache misses, fetches, pipeline stalls, thread context switching, and many other subtle aspects of microprocessors.