Design And Analysis For High Performance Switching Fabric In High-radix Router

It has been expected that the peak performance of the next generation highperformance computer (HPC) should rise to EFLOPS scale. It is a great challenge todesign the next generation high performance interconnection network and router. Highradix routers, which integrate more interconnection ports in one chip, outperforme withless network diameter, higher network bandwidth and higher robust, lower cost andlower power consumption, but also lead to some new problems. First, more ports andhigher bandwidth also mean more resource needed, it is difficult to elimilate HOL effectand design a high throughput switching fabric with limited resource. Second, more portsalso result in complicated chip design, structural and scalable design should be done torelease the pressure on backend floorplan and wire routing.Merits and demrits of some traditional switching fabrics have been analyzed in thepaper, especially the YARC switching fabric. YARC is the inaugurator in high radixrouter design, which has integrate64network ports, open the door to high radix routerdesign and implementation, so swiching fabric, structural design and processingpipeline of YARC are introduced in detail. We focus on high throughput high radixrouter design in this paper. A new switching fabric based on asymmetric crossbar isannounced. Asymmetic crossbar is a crossbar with much less input ports than outputports. RTL simulation reveals that asymmetric crossbar can elimilate HOL effect in thefabric and leads to much high throughput. Structural and TILE-based design of thisfabric is also instroduced.Some high radix switching fabrics, not only the asymmetric crossbar based fabric,but also some other fabric,such as one-level32×32crossbar fabric and two YARC-likeTILE-based fabrics, have been implemented in RTL coding. All these fabrics aredesigned in a uniform framework, which uses some common and scalable designmodules to simplify logic design. Some key modules, such as request generator, arbiterand credit based flow controller, have been introduced detailly. A testbed for high radixswitching fabric has been implemented, which supports mutli-round loop testing andcan vary and test many parameters in an automatic mode.