Full-System Simulator for IBM PowerPC 970

• Functional-only simulation: Purely functional simulation models the effects of instructions without modeling the time it takes to execute these instructions. Functional-only simulation assumes that each instruction requires one cycle to execute. Memory accesses are synchronous and instantaneous. This simulation model is useful for software development and debugging when a precise measure of execution time is not significant. Functional simulation is also useful for reaching a specific state or threshold in a simulation.
• Performance simulation: For accurate performance evaluation, the Full-System Simulator provides performance simulation (also referred to as timing simulation.) A performance simulation model represents internal policies and mechanisms for system components, such as arbiters, queues, and pipelines. Each operation takes a number of cycles to complete and accounts for both processing time and resource constraints. Performance simulation models have been correlated against hardware or other references to acceptable levels of tolerance.

The Full-System Simulator can also be configured to fast-forward the simulation, using a functional model to a specific point of interest in the application, and then switch to a timing-accurate mode to conduct performance studies. Various types of operational details can then be gathered in order to gain insight into the behavior of real-world hardware and software systems. This affords a high level of configurability: Users can dynamically trade timing accuracy and detail for faster simulation speed.