Dynamically Programmable Gate Arrays: A Step Toward Increased Computational Density

Article by André DeHon published in Proceedings of the Fourth Canadian Workshop on Field-Programmable Devices (FPD'96, May, 1996), p. 47 ff.

Field-Programmable Gate Arrays are interesting, general-purpose computational devices because (1) they have high computational density and (2) they have fine-grained control of their computational resources since each gate is independently controlled. The earlier provides them with a potential 10x advantage in raw peak performance density versus modern microprocessors. The later can afford a 32x advantage on random bit-level computations. Nonetheless, typical FPGA usage seldom extracts this full density advantage. DPGAs are less computationally dense than FPGAs, but allow most applications to achieve greater, yielded computational density. The key to unraveling this potential paradox lies in distinguishing instruction density from active computing density. Since the storage space for a single instruction is inherently smaller than the computational element it controls, packing several instructions per computational unit increases the aggregate instruction capacity of the device without a significant reduction in computational density. The number of different instructions executed per computational task often limits the effective computational density. As a result, DPGAs can meet the throughput requirements of many computing tasks with 3-4x less area than conventional FPGAs.