ABSTRACT

Alpha consistency, a formal definition of the shared memory model of DEC-Alpha based multiprocessors, is defined in the framework of [6]. The definition allows arbitrary out-of- order execution of instructions and is convenient for use by programmers. Several programming techniques that allow to run programs written assuming sequentially consistent hardware on alpha consistent hardware are presented. First, it is shown that every data-race free program runs on an al- pha consistent memory as if it was sequentially consistent. Second, it is shown how to transform any non-cooperative solution for the mutual exclusion problem based on sequen- tial consistency into a solution based on alpha consistency. Finally, it is shown that this general method is not optimal; for two well-known mutual exclusion algorithms, a specific analysis of the code yields a more efficient algorithm.