In 1971 NASA Goddard Space Flight Center initiated a program to develop high-speed image processing systems. These systems use thousands of processing elements (PE's) operating simultaneously to achieve their speed (massive parallelism). A typical satellite image contains millions of picture elements (pixels) that can generally be processed in parallel. In 1979 a contract was awarded to construct a massively parallel processor (MPP) to be delivered in 1982. The processor has 16,896 PE's arranged in a 128-row by 132-column rectangular array. The PE's are in the array unit (Figure 1). Other major blocks in the massively parallel processor are the array control unit, the staging memory, the program and data management unit, and the interface to a host computer.