Specially-Designed Out-of-Order Processor Architecture for Microcontrollers

Abstract

In very large-scale integration circuit (VLSI) systems, microcontrollers are often implanted to manage the whole system to complete the given computing tasks. They play an essential part as regulators, which should allocate resources steadily and issue instructions promptly to drive functional units. However, most of the recent research focuses on the operation at the software level or the scheduling at the SoC level, ignoring the impact of the microarchitecture and the features of controlled sub-modules. This paper analyzes the requirements of microcontrollers in the VLSI system with various constraints and conditions that should be considered in the hardware implementation of such microarchitecture. Furthermore, this paper takes an open-source design using RISC-V ISA as the prototype to implement hardware microarchitecture. This design integrates the techniques of out-of-order processing, which are usually used on superscalar processors. As a result, the design quadruples the number of pipelined instructions, greatly alleviating the stalling of the instruction stream with a maximum extra look up table utilization of 18.37% in FPGA implementation.