Frequency Optimization Objective during System Prototyping on Multi-FPGA Platform

Multi-FPGA hardware prototyping is becoming increasingly important in the system on chip design cycle. However, after partitioning the design on the multi-FPGA platform, the number of inter-FPGA signals is greater than the number of physical connections available on the prototyping board. Therefore, these signals should be time-multiplexed which lowers the system frequency. The way in which the design is partitioned affects the number of inter-FPGA signals. In this work, we propose a set of constraints to be taken into account during the partitioning task. Then, the resulting inter-FPGA signals are routed with an iterative routing algorithm in order to obtain the best multiplexing ratio. Indeed, signals are grouped and then routed using the intra-FPGA routing algorithm: Pathfinder. This algorithm is adapted to deal with the inter-FPGA routing problem. Many scenarios are proposed to obtain the most optimized results in terms of prototyping system frequency. Using this technique, the system frequency is improved by an average of 12.8% compared to constructive routing algorithm. 1. Introduction With the ever increasing complexity of system on chip circuits, the software and hardware developers can no longer wait for the fabrication phase to test their designs [1]. Currently, it is estimated that 60 to 80 percent of an ASIC design is spent in performing verification [2]. FPGA-based prototyping is an important step in the creation of the final product and it is the key to the success of marketing in time. The key advantage of FPGA-based prototyping is the ability to run at high speed (sometimes at almost real-time speed) a cycle-accurate, bit-accurate model of the SoC [3]. The availability of automatic FPGA mapping tools has streamlined the design conversion process, making the path from ASIC design to FPGA implementation more straightforward. When the logic capacity of a single FPGA is less than the size of the design under test, a multi-FPGA platform is used to map the entire design. Because the silicon area overhead of FPGA versus ASIC technology has been measured to be about 40x [4], FPGA programming technology requires that an ASIC logic design be partitioned across multiple FPGA devices to achieve the necessary device logic capacity. The number of FPGAs depends on the size of the prototyping system, ranging from a few [5] up to 60 FPGAs [6]. In order to map the design into a multi-FPGA board, a partitioning tool decomposes the design into pieces that will fit within the logic resources of individual FPGA devices. Partitioning is often performed to