Our results indicate that the benefits of the extensions are limited. Read-broadcast reduces the number of invalidation misses, but at a high cost in processor lockout from the cache. The net effect can be an increase in total execution cycles. Competitive snooping benefits only those programs with high per processor locality of reference to shared data. For programs characterized by inter-processor contention for shared addresses, competitive snooping can degrade performance by causing a slight increase in bus utilization and total execution time.