Accelerated FPGA architecture design: Capabilities and limitations of analytical models

FPGA architects typically use experimental techniques to design new architectures. These techniques are time consuming, thus limiting the number of the architectures that can be investigated. Some previous works use analytical models to significantly accelerate the design of a new architecture. To properly capitalize on the benefits of the analytical models, the designers need to have an understanding of the capabilities and the limitations of the analytical models. In this paper, we use two representative architecture questions to provide such understanding. These two questions respectively investigate the optimization of a general-purpose FPGA architecture and the optimization of an application-specific FPGA architecture. For an optimized general purpose architecture, we show that the conclusions made by the analytical models are similar to the experimental techniques, with respect to three different design goals: area, delay and area-delay trade-off. This justifies the use of the analytical models in optimizing general-purpose FPGA architectures. We also find that the analytical models can not capture the behavior of `some´ applications that contain `discrete effects´. We present this later finding and the related explanations to show that the analytical models can not optimize application-specific architectures in some cases.