Pipeline Stage Resolved Timing Characterization of FPGA and ASIC Implementations of a RISC V Processor

TL;DR

This paper introduces a pipeline stage resolved timing analysis framework for a RISC V processor, enabling detailed comparison of FPGA and ASIC implementations at the microarchitectural level.

Contribution

It presents a unified analysis method that decomposes timing paths into components and maps them to pipeline stages, revealing fundamental differences between FPGA and ASIC timing behaviors.

Findings

FPGA timing dominated by routing parasitics and variability.

ASIC timing governed by logic depth and parametric variation.

Pipeline stage analysis identifies platform-specific timing bottlenecks.

Abstract

This paper presents a pipeline stage resolved timing characterization of a 32-bit RISC V processor implemented on a 20 nm FPGA and a 7 nm FinFET ASIC platform. A unified analysis framework is introduced that decomposes timing paths into logic, routing, and clocking components and maps them to well-defined pipeline stage transitions. This approach enables systematic comparison of timing behavior across heterogeneous implementation technologies at a microarchitectural level. Using static timing analysis and statistical characterization, the study shows that although both implementations exhibit dominant critical paths in the EX to MEM pipeline transition, their underlying timing mechanisms differ fundamentally. FPGA timing is dominated by routing parasitics and placement dependent variability, resulting in wide slack distributions and sensitivity to routing topology. In contrast, ASIC timing is governed primarily by combinational logic depth and predictable parametric variation across process, voltage, and temperature corners, yielding narrow and stable timing distributions. The results provide quantitative insight into the structural origins of timing divergence between programmable and custom fabrics and demonstrate the effectiveness of pipeline stage resolved analysis for identifying platform specific bottlenecks. Based on these findings, the paper derives design implications for achieving predictable timing closure in processor architectures targeting both FPGA and ASIC implementations.