Abstract: In a multiprocessor system, a conflict checking mechanism is implemented in the L2 cache memory. Different versions of speculative writes are maintained in different ways of the cache. A record of speculative writes is maintained in the cache directory. Conflict checking occurs as part of directory lookup. Speculative versions that do not conflict are aggregated into an aggregated version in a different way of the cache. Speculative memory access requests do not go to main memory.

Abstract: In a multiprocessor system with speculative execution, atomicity can be approached in several fashions. One approach is to have atomic instructions that achieve multiple functions and are guaranteed to complete. Another approach is to have blocks of code that are grouped to succeed or fail together. A system can incorporate more than one such approach. In implementing more than one approach, the system may prioritize one over another. When conflict detection is done through a directory lookup in cache memory, atomic instructions and atomicity related operations may be implemented in a cache data array access pipeline in that cache memory. This implementation may include feedback to the pipeline for implementing multiple functions within an atomic instruction and also for cascading atomic instructions.