Simulation models for the reliability and performance evaluation of degradable multiprocessor systems are presented. Three types of multiprocessors are studied based on three general interconnection topologies, namely, crossbar, multistage interconnection network (MIN) and multiple-bus. The models support graceful degradation by considering processor, memory and interconnection network switch failures. The models are also extended to estimate the Bandwidth availability for the three architectures by computing the bandwidth of the truncated systems. Typical results indicate that multiple-bus performs the best and the MIN performs the worst under degraded modes.