Design Principles for Synthesizable Processor Cores

As FPGAs get more competitive, synthesizable processor cores become an attractive choice for embedded computing. Currently popular commercial processor cores do not fully exploit current FPGA architectures. In this paper, we propose general design principles to increase instruction throughput on FPGA-based processor cores: first, superpipelining enables higher-frequency system clocks, and second, predicated instructions circumvent costly pipeline stalls due to branches.

To evaluate their effects, we develop Tinuso, a processor architecture optimized for FPGA implementation. We demonstrate through the use of micro-benchmarks that our principles guide the design of a processor core that improves performance by an average of 38% over a similar Xilinx MicroBlaze configuration.