The new generation of domain-specific AI accelerators is characterized by rapidly increasing demands for bulk data transfers, as opposed to small, latency-critical cache line transfers typical of traditional cache-coherent systems. In this paper, we address this critical need by introducing the FlooNoC Network-on-Chip (NoC), featuring very wide, fully Advanced eXtensible Interface (AXI4) compliant links designed to meet the massive bandwidth needs at high energy efficiency. At the transport level, non-blocking transactions are supported for latency tolerance. Additionally, a novel end-to-end ordering approach for AXI4, enabled by a multi-stream capable Direct Memory Access (DMA) engine simplifies network interfaces and eliminates inter-stream dependencies. Furthermore, dedicated physical links are instantiated for short, latency-critical messages. A complete end-to-end reference implementation in 12nm FinFET technology demonstrates the physical feasibility and power performance area (PPA) benefits of our approach. Utilizing wide links on high levels of metal, we achieve a bandwidth of 645 Gbps per link and a total aggregate bandwidth of 103 Tbps for an 8x4 mesh of processors cluster tiles, with a total of 288 RISC-V cores. The NoC imposes a minimal area overhead of only 3.5% per compute tile and achieves a leading-edge energy efficiency of 0.15 pJ/B/hop at 0.8 V. Compared to state-of-the-art NoCs, our system offers three times the energy efficiency and more than double the link bandwidth. Furthermore, compared to a traditional AXI4-based multi-layer interconnect, our NoC achieves a 30% reduction in area, corresponding to a 47% increase in GFLOPSDP within the same floorplan.

翻译：新一代领域专用AI加速器的特点是对批量数据传输的需求快速增长，这与传统缓存一致性系统中典型的、对延迟敏感的小型缓存行传输形成鲜明对比。本文通过引入FlooNoC片上网络（NoC）来应对这一关键需求，该网络采用极宽且完全符合高级可扩展接口（AXI4）标准的链路，旨在以高能效满足巨大的带宽需求。在传输层，支持非阻塞事务以实现延迟容忍。此外，一种新颖的、由支持多流的直接内存访问（DMA）引擎实现的端到端AXI4排序方法简化了网络接口并消除了流间依赖。同时，为短且对延迟关键的消息实例化了专用物理链路。在12nm FinFET工艺中的完整端到端参考实现展示了我们方法的物理可行性与功耗-性能-面积（PPA）优势。通过在高层金属上使用宽链路，我们实现了每链路645 Gbps的带宽，以及一个包含288个RISC-V核心的8x4处理器集群网格总计103 Tbps的聚合带宽。该NoC仅给每个计算单元带来3.5%的极小面积开销，并在0.8 V电压下实现了领先的0.15 pJ/B/跳的能效。与最先进的NoC相比，我们的系统能效提高了三倍，链路带宽提高了一倍以上。此外，与传统的基于AXI4的多层互连相比，我们的NoC实现了30%的面积缩减，相当于在相同版图内GFLOPSDP提升了47%。