Customizing the Datapath and ISA of Soft VLIW Processors

Abstract

In this paper, we examine the trade-offs in performance and area due to customizing the datapath and instruction set architecture of a soft VLIW processor implemented in a high-density FPGA. In addition to describing our processor, we describe a number of microarchitectural optimizations we used to reduce the area of the datapath. We also describe the tools we developed to customize, generate, and program our processor. Our experimental results show that datapath and instruction set customization achieve high levels of performance, and that using on-chip resources and implementing microarchitectural optimizations like selective data forwarding help keep FPGA resource utilization in check.