Simultaneous short-path and long-path timing optimization for FPGAs

Abstract

This work presents the routing cost valleys (RCV) algorithm - the first published algorithm that simultaneously optimizes all short- and long-path timing constraints in a field-programmable gate array (FPGA). RCV is comprised of a new slack allocation algorithm that produces both minimum and maximum delay budgets for each circuit connection, and a new router that strives to meet and, if possible, surpass these connection delay constraints. RCV achieves excellent results. On a set of 100 large circuits, RCV improves both long-path and short-path timing slack significantly vs. an earlier computer-aided design (CAD) system that focuses solely on long-path timing. Even with no short-path timing constraints, RCV improves the clock speed of circuits by 3.9% on average. Finally, RCV is able to meet timing on all 72 peripheral component interconnect (PCI) cores tested, while an earlier algorithm fails to achieve timing on all 72 cores.