Steiglitz The research is on the limits of scalable special-purpose architectures for highly parallel computation, especially computation on regular arrays. Important applications of array- based computation can be found in digital signal processing, and in many areas of scientific computation, including many-body problems with gravitational or coulombic interactions, fluid dynamics, and wave propagation. These applications require highly parallel computation either because of the need for real- time operation, or because the total number of operations required is very large. The basic problems being addressed are: 1. The design and reliability analysis of large fault-tolerant arrays, and on-line reconfiguration and error-detection algorithms for these special-purpose architectures; 2. The design and analysis of reliable clocking schemes for very large arrays of processors, especially the comparison of synchronous, self-timed, and hybrid clocking; 3. A study of the general issue of cost-effective scaling of large, special-purpose computer architectures for regular computations; and, 4. Extension of the work to Hierarchical Data Computations, such as those in the fast monopole and multipole methods for many-body problems, where particles are distributed in space, and are clustered by decomposing space into hierarchical domains.