VSIM - A Superscalar CPU Simulator

The simulator described in this paper is able to model five recent superscalar microprocessors (Compaq Alpha 21264, Hewlett-Packard PA-8500, IBM Power3, Intel Pentium Pro/II/III, MIPS R10000), while providing instruction shelving, dynamic register renaming, out-of-order issue and instruction reordering. VSIM simulates branch prediction and the operation of caches using a unique parameter driven black box approach called impact modeling. VSIM provides two modes of operation: in education mode, internal operations of recent superscalars are visualized by running user-defined assembly programs, while VSIM’s performance simulation mode allows for the assessment of various implementation alternatives, optimization of key design parameters and identification of performance bottlenecks of microarchitectures. In this mode the simulated processor runs user-definable synthetic workloads. The ‘Generic’ workload follows the dynamic instruction distribution of the SPEC95 benchmark suite, thus the performance results obtained are in line with SPEC benchmark results. In addition, several preset workloads enable the analysis of the selected CPU in different application environments. The simulator has been thoroughly validated for both internal operation and accuracy of performance assessment.