Cyclist: Accelerating hardware development

Abstract

The end of Dennard scaling has led to an increase in demand for energy-efficient custom hardware accelerators, but current hardware design is slow and laborious, partly because each iteration of the compile-run-debug cycle can take hours or even days with existing simulation and emulation platforms. Cyclist is a new emulation platform designed specifically to shorten the total compile-run-debug cycle. The Cyclist toolflow converts a Chisel RTL design to a parallel dataflow graph, which is then mapped to the Cyclist hardware architecture, consisting of a tiled array of custom parallel emulation engines. Cyclist provides cycle-accurate/bit-accurate RTL emulation at speeds approaching FPGA emulation, but with compile time closer to software simulation. Cyclist provides full visibility and debuggability of the hardware design, including moving forwards and backwards in simulation time while searching for trigger events. The snapshot facility used for debugging is also used to provide a “pay-as-you-go” mapping strategy, which allows emulation to begin execution with a low-effort placement, while higher-quality emulation placements are optimized in the background and swapped in to a running emulation. The Cyclist ASIC design requires 0.069mm2 per tile and runs at 2GHz in a 45nm CMOS process. Our evaluation demonstrate that Cyclist outperforms FPGA emulation, VCS, and C+,+, simulation on combined compile and run time for up to a billion cycles for a set of real-world hardware benchmarks.