Scalable High-Radix Modular Crossbar Switches

Crossbars are a basic building block of networks on chip that can be used as fast, single-stage networks or in router cores for larger scale networks. However, scaling crossbars to high radices presents a number of efficiency, performance, and area challenges. Thus, we propose modular flow-through crossbar switch cores that perform better at high radices than conventional monolithic designs. The modular sub-blocks are arranged in a controlled flow-through, pipelined scheme to eliminate global connections and maintain linear performance scaling and high throughput. Modularity also enables energy savings via deactivation of unused I/O wires. Evaluation using an analytical crossbar switch modeling tool demonstrated improved energy delay product (up to 5.3X) compared to conventional crossbar switches, but with approximately 30% area overhead. Further, we evaluated modular crossbar networks with the proposed switch cores using BookSim2, cycle-accurate detailed network on chip tool. The proposed design achieves more than 90% saturation capacity with an internal speed up of 1.5, supports data line rates as high as 102.4Gbps (in 40nm CMOS bulk), and offers lower average network latency compared to conventional crossbars.