gem5
General Execution-driven Multiprocessor Simulator (GEMS).
GEMS is a set of modules for Virtutech Simics that enables detailed simulation of multiprocessor systems, including Chip-Multiprocessors (CMPs).
The gem5 simulator is a modular platform for computer-system architecture research, encompassing system-level architecture as well as processor microarchitecture.
gem5 is a community led project with an open governance model.