Full system simulation

A computer architecture simulator, or an architectural simulator, is a piece of software to model computer devices (or components) to predict outputs and performance metrics on a given input. An architectural simulator can model a target microprocessor only (see instruction set simulator), or an entire computer system (see full system simulator) including a processor, a memory system, and I/O devices.

A full-system simulator is an architecture simulator that simulates an electronic system at such a level of detail that complete software stacks from real systems can run on the simulator without any modification. A full system simulator effectively provides virtual hardware that is independent of the nature of the host computer. The full-system model typically has to include processor cores, peripheral devices, memories, interconnection buses, and network connections.

The defining property of full-system simulation compared to an instruction set simulator is that the model allows real device drivers and operating systems to be run, not just single programs. Thus, full-system simulation makes it possible to simulate individual computers and networked computer nodes with all their software, from network device drivers to operating systems, network stacks, middleware, servers, and application programs.

A cycle-accurate simulator is a computer program that simulates a microarchitecture on a cycle-by-cycle basis. In contrast an instruction set simulator simulates an instruction set architecture usually faster but not cycle-accurate to a specific implementation of this architecture; they are often used when emulating older hardware, where time precisions are very important from legacy reasons. 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.

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