In a recent paper. Pfister and Norton[4] brought to our attention the potential degradation in performance of multi-stage interconnection networks in the presence of nonuniform traffic patterns. More specifically, they studied the effect of a single hot spot - a location that is accessed more frequently - in an otherwise uniform traffic environment. Their simulations assumed that all input lines contribute to the hot spot. Their results showed that the effect of hot spots drastically reduced the bandwidth of the network. In this note. we confirm Pfister and Norton's results and present supplemental data and arguments which illustrate other aspects of hot spot contention. In particular, we show that the performance improves when the source of the hot spot is more localized.
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