Abstract: A method and apparatus for conditional memory ordering are disclosed. The cost of memory ordering is reduced by determining circumstances in which a memory ordering operation is unnecessary and avoiding the overheads of these operations by reducing the frequency of invoking hardware memory ordering mechanisms. Hardware instructions for implementing a conditional memory ordering method and apparatus is described which may be implemented in a multiprocessor environment. The conditional memory ordering instruction executes locally using a release vector containing release numbers for each processor in the system. The instruction first determine whether a processor identifier of the release number is associated with the current processor. Where it is not, a conditional registered is examined and appropriate remote synchronization operations are commanded where necessary.