Scalable register bypassing for FPGA-based processors

In this paper, a scalable scheme, configurable via register-transfer level parameters, for full register bypassing in a modern embedded processor architecture, termed ByoRISC, is presented. The register bypassing specification is parameterized regarding the number of homogeneous register file read and write ports and the number of pipeline stages of the processor. The performance characteristics (cycle time, chip area) of the proposed technique have been evaluated for FPGA target implementations of the synthesizable ByoRISC model. It is proved that, a full bypassing network is a viable solution for the elimination of data hazards when servicing instructions with multiple read and write operands. While the maximum clock frequency is reduced by 17.9% in average, when using partial versus full forwarding, the positive effect of custom computation eliminates this effect by providing cycle speedups of 3.9× to 5.5× and corresponding execution time speedups for a ByoRISC testbed processor of 3.6×. Individual application speedups of up to 9.4× have also been obtained.