Interconnect Customization for a Hardware Fabric

This article describes several multiplexer-based interconnection strategies designed to improve energy consumption of stripe-based coarse-grain reconfigurable fabrics. Application requirements for the architecture as well as two dense subgraphs are extracted from a suite of signal and image processing benchmarks. These statistics are used to drive the strategy of the composition of multiplexer-based interconnect. The article compares interconnects that are fully connected between stripes, those with a cardinality of 8: 1 to 4: 1, and extensions that provide a 5: 1 cardinality, limited 6: 1 cardinality, and hybrids between 5: 1 and 3: 1 cardinalities. Additionally, dedicated vertical routes are considered replacing some computational units with dedicated pass-gates. Using a fabric interconnect model (FIM) written in XML, we demonstrate that fabric instances and mappers can be automatically generated using a Web-based design flow. Upon testing these instances, we found that using an 8: 1 cardinality interconnect with 33% of the computational units replaced with dedicated pass-gates provided the best energy versus mappability tradeoff, resulting in a 50% energy improvement over fully connected rows and 20% energy improvement over an 8: 1 cardinality interconnect without dedicated vertical routes.