Functional verification of the POWER4 microprocessor and POWER4 multiprocessor systems

This paper describes the methods and simulation techniques used to verify the microarchitecture design and functional performance of the IBM POWER4 processor and the POWER4-based Regatta system. The approach was hierarchical, based on but considerably expanding the practice used for verification of the CMOS-based IBM S/390 Parallel Enterprise Server(TM) G4. For POWER4, verification began at the abstract, high-level design phase and continued throughout the designer and unit levels, the multi-unit level, and finally the multiple-chip system level. The abstract (high-level design) phase permitted early validation of the POWER4 processor design prior to its commitment to HDL. The designer and unit-level stages focused on ensuring the correctness of the microarchitectural components. Multi-unit-level verification, performed on storage and I/O components as well as on the processor, confirmed architectural compliance for each of the chips and subsystems. Finally, system-level verification tested multiprocessor coherence and system-level function, including processor-to-I/O communication and validation of multiple hardware configurations. In parallel with design and functional validation, verification of reliability functions, performance, and degraded configurations was also performed at most of the levels in the hierarchy.