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.