Impact of Memory Architecture on FPGA Energy Consumption

FPGAs have the advantage that a single component can be configured post-fabrication to implement almost any computation. However, designing a one-size-fits-all memory architecture causes an inherent mismatch between the needs of the application and the memory sizes and placement on the architecture. Nonetheless, we show that an energy-balanced design for FPGA memory architecture (memory block size(s), memory banking, and spacing between memory banks) can guarantee that the energy is always within a factor of 2 of the optimally-matched architecture. On a combination of the VTR 7 benchmarks and a set of tunable benchmarks, we show that an architecture with internally-banked 8Kb and 256Kb memory blocks has a 31% worst-case energy overhead (8% geomean). In contrast, monolithic 16Kb memories (comparable to 18Kb and 20Kb memories used in commercial FPGAs) have a 147% worst-case energy overhead (24% geomean). Furthermore, on benchmarks where we can tune the parallelism in the implementation to improve energy (FFT, Matrix-Multiply, GMM, Sort, Window Filter), we show that we can reduce the energy overhead by another 13% (25% for the geomean).