The availability of high‐performance, low‐cost processing hardware provides the basis for very powerful programmable signal processing machines. A wide spectrum of machine architectures is available to the system designer. However, since these often have striking functional differences, the selection process must involve much more than a simplistic comparison of processing power. This paper compares the characteristics of generic special‐purpose and general‐purpose signal processors to emphasize critical differences. These differences are further illuminated in the descriptions of two high‐performance machines — one a special‐purpose programmable signal processor and the other a general‐purpose scientific “supercomputer.” Included in the descriptions are the approaches used in each machine for primitive operations, processing sequence control, data input and data transfer methodology, and method of achieving high‐speed operation.