What is perhaps most interesting about the results is the poor sustainable memory bandwidth of the hierarchical memory machines. The actual values obtained from user code are often only a small fraction of the impressive ``peak'' bandwidth numbers stated by a number of vendors. Unfortunately, even ``peak bandwidth'' numbers are stated by so few vendors that it is not possible to do a comprehensive survey of the ratio of ``peak'' to ``sustainable'' bandwidth.
In order to make some sense of the diversity of the numbers, the machines have been divided up into various categories based on their memory system type. The four categories used here are: Vector, Shared-memory (non-vector), Uniprocessor, and Distributed Memory. Selected results are presented in the following sections.