Modeling and simulation/emulation play a major role in research and development of novel Networks-on-Chip (NoCs). However, conventional software simulators are so slow that studying NoCs for emerging many-core systems with hundreds to thousands of cores is challenging. State-of-the-art FPGA-based NoC emulators have shown great potential in speeding up the NoC simulation, but they cannot emulate large-scale NoCs due to the FPGA capacity constraints. Moreover, emulating large-scale NoCs under synthetic workloads on FPGAs typically requires a large amount of memory and thus involves the use of off-chip memory, which makes the overall design much more complicated and may substantially degrade the emulation speed. This article presents methods for fast and cycle-accurate emulation of NoCs with up to thousands of nodes using a single FPGA. We first describe how to emulate a NoC under a synthetic workload using only FPGA on-chip memory (BRAMs). We next present a novel use of time-division multiplexing where BRAMs are effectively used for emulating a network using a small number of nodes, thereby overcoming the FPGA capacity constraints. We propose methods for emulating both direct and indirect networks, focusing on the commonly used meshes and fat-trees (
k
-ary
n
-trees). This is different from prior work that considers only direct networks. Using the proposed methods, we build a NoC emulator, called FNoC, and demonstrate the emulation of some mesh-based and fat-tree-based NoCs with canonical router architectures. Our evaluation results show that (1) the size of the largest NoC that can be emulated depends on only the FPGA on-chip memory capacity; (2) a mesh-based NoC with 16,384 nodes (128×128 NoC) and a fat-tree-based NoC with 6,144 switch nodes and 4,096 terminal nodes (4-ary 6-tree NoC) can be emulated using a single Virtex-7 FPGA; and (3) when emulating these two NoCs, we achieve, respectively, 5,047× and 232× speedups over BookSim, one of the most widely used software-based NoC simulators, while maintaining the same level of accuracy.
State-of-the-art studies show that FPGA-based hardware merge sorters (HMSs) can achieve superior performance compared with optimized algorithms on CPUs and GPUs. The performance of any HMS is proportional to its operating frequency (F) and the number of records that can be output each cycle (E). However, all existing HMSs have a problem that F drops significantly with increasing E due to the increase of the number of levels of gates. In this paper, we propose novel architectures for HMSs where the number of levels of gates is constant when E is increased. We implement some HMSs adopting the proposed architectures on a Virtex-7 FPGA. The evaluation shows that an HMS of E = 32 operates at 311MHz and achieves 3.13x higher throughput than the state-of-the-art HMS.
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