This thesis is a comparative study of three computer system simulators. These computer programs are commonly used to test the efficiency and feasibility of new computer architectures, as well for debugging and testing software. With this study, we evaluate the fundamental differences of three simulators: SimICS, SimpleScalar and ML-RSIM. A comprehensive study of simulation techniques is presented, and each evaluated simulator is classified using those premises. Quantification the performance differences using a benchmark suite is made. The results show that the most feature-rich of the simulators also seems to have the highest performance in the group.