Verilator

Verilator is a free and open source software tool which converts Verilog (a hardware description language) to a cycle-accurate behavioral model in C++ or SystemC. It is restricted to modeling the synthesizable subset of Verilog and the generated models are cycle-accurate, 2-state, with synthesis (zero delay) semantics. As a consequence the models typically offer higher performance than the more widely used event driven simulators, which can process the entire Verilog language and model behavior within the clock cycle. Verilator is now used within academic research, open source projects and for commercial semiconductor development. It is part of the growing body of free EDA software.