Timing optimization of FPGA placements by logic replication

Abstract

Logic replication for placement level timing optimization is studied in the context of FPGAs. We make the observation that critical paths are dominated by interconnect delay and are frequently highly circuitous. We propose a systematic replication technique to “straighten ” such paths. The resulting algorithm has several components: cell selection, slot selection for a duplicate cell, fanout partitioning and placement legalization. This algorithm is described and promising preliminary experimental results are reported with up to 29 % improvement in critical path delay.