A fault-tolerant communication scheme that facilitates near-optimal routing and broadcasting in hypercube computers subject to node failures is described. The concept of an unsafe node is introduced to identify fault-free nodes that may cause communication difficulties. It is shown that by only using 'feasible' paths that try to avoid unsafe nodes, routing and broadcasting can be substantially simplified. A computationally efficient routing algorithm that uses local information is presented. It can route a message via a path of length no greater than p+2, where p is the minimum distance from the source to the destination, provided that not all nonfaulty nodes in the hypercube are unsafe. Broadcasting can be achieved under the same fault conditions with only one more time unit than the fault-free case. The problems posed by deadlock in faulty hypercubes are discussed, and deadlock-free implementations of the proposed communication schemes are presented.>

Prefetching techniques in disk caching are addressed. An adaptive prefetch design based on a run-time caching statistics of files is presented. Cache hit histories produced by prefetching are used as a measure of the file access sequentialities. Detailed cache design analysis is discussed using simulation results of a trace-driven model with traces collected from a personal system. The curves obtained from the adaptive design, although not the best at every point, track very well with the best curve in each operation. This shows the dynamic intelligence and efficiency of the file-based adaptive prefetching. The file-based design is compared with one that uses the same transition diagram on disk access but without file identification. The file-based adaptive design outperforms the non-file-based one consistently under all cache sizes.>