According to the present invention, methods and apparatus are provided for increasing the efficiency of data access in a multiple processor, multiple cluster system. Mechanisms for transmitting memory cancels to memory controllers in the various clusters of a multiple cluster system are provided. In one example, memory cancels are transmitted between clusters when it is determined that a memory line associated with a probe is dirty. The memory cancel directs the memory controller to no longer proceed with a data fetch from main memory. In another example, memory cancels are transmitted at a home cluster based on information in a coherence directory in order to more quickly end a data fetch.