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As multi/many-core architectures evolve, the demands on the network-on-chip (NoC) are amplified. In addition to high performance and physical scalability, the NoC is increasingly required to also provide specialized functionality, such as network virtualization, flow isolation, and quality-of-service. Although traditional architectures supporting virtual channels (VCs) offer the resources for flow partitioning and isolation, an adversarial workload can still interfere and degrade the performance of other workloads that are active in a different set of VCs. In this paper, we present PhaseNoC, a truly noninterfering VC-based architecture that adopts time-division multiplexing at the VC level. Distinct flows, or application domains, mapped to disjoint sets of VCs are isolated, both inside the router's pipeline and at the network level. Any latency overhead is minimized by appropriate scheduling of flows in separate phases of operation, irrespective of the chosen topology. When strict isolation is not required, the proposed architecture can employ opportunistic bandwidth stealing. This novel mechanism works synergistically with the baseline PhaseNoC techniques to improve the overall latency/throughput characteristics of the NoC, while still preserving performance isolation. Experimental results corroborate that—with lower cost than state-of-the-art NoC architectures, and with minimum latency overhead—PhaseNoC removes any flow interference and allows for efficient network traffic isolation.

Early estimation of the peak power consumption of a system under development is crucial in assessing the design's reliability and thermal profile, and for benchmarking various architectural options and chip-level power management features. In this paper, we present a versatile power-virus generation technique for Networks-on-Chip (NoC), which allows the designer to quantify the realistically attainable peak power consumption, in order to efficiently guide the design process. The proposed PowerMax methodology generates appropriate network traffic patterns that cause peak power consumption within the NoC. More importantly, PowerMax is a fully automated high-level methodology that can be applied to any network topology and any routing algorithm. The proposed technique maximizes both the network utilization and the data switching activity, thereby causing, on average, 5.5x higher power consumption than synthetic traffic patterns with random behavior. PowerMax can be used as a stand-alone tool to test the power characteristics of the NoC, or it can be embedded in other system-level powervirus applications.

2015-April 1090 1095

As multicore systems transition to the many-core realm, the pressure on the interconnection network is substantially elevated. The network on chip (NoC) is expected to undertake the expanding demands of the ever-increasing numbers of processing elements, while its area/power footprint remains severely constrained. Hence, low-cost NoC designs that achieve high-throughput and low-latency operation are imperative for future scalability. While the buffers of the NoC routers are key enablers of high performance, they are also major consumers of area and power. In this paper, we extend elastic buffer (EB) architectures to support multiple virtual channels (VCs), and we derive ElastiStore , a novel lightweight EB architecture that minimizes buffering requirements without sacrificing performance. ElastiStore uses just one register per VC and a shared buffer sized large enough to merely cover the round-trip time that appears either on the NoC links or due to the internal pipeline of the NoC routers. The integration of the proposed EB scheme in the NoC router enables the design of efficient architectures, which offer the same performance as baseline VC-based routers, albeit at a significantly lower cost. Cycle-accurate network simulations including both synthetic traffic patterns and real application workloads running in a full-system simulation framework verify the efficacy of the proposed architecture. Moreover, the hardware implementation results using a 45-nm standard-cell library demonstrate ElastiStore’s efficiency.

Network-on-Chip (NoC) design tries to keep a balance between network performance and physical implementation flexibility. The adoption of Virtual Channels (VC) holds promise for scalable NoC design. VCs allow for traffic separation and isolation, enable deadlock avoidance and improve network performance. In this paper, we present ElastiNoC, a novel distributed VC-based router architecture that enjoys all the benefits offered by VCs and leads to efficient silicon-aware implementations. The proposed architecture utilizes an efficient buffering strategy and allows for modular pipelined organizations that increase the clock frequency. Moreover, it offers maximum freedom in terms of physical placement, by allowing the NoC components to be physically spread throughout the chip, irrespective of the network topology. The combined effect of all supported features enables significant delay reductions under equal performance, when compared to state-of-the-art VC-based NoC implementations. Moreover, the careful addition of self-test structures allows ElastiNoC to enjoy fully distributed Built-In Self Testability (BIST), where testing unfolds in phases and reaches high fault coverage with small test application time.

Elastic systems operate in a dataflow-like mode using a distributed scalable control and tolerating variable-latency computations. At the same time, multithreading increases the utilization of processing units and hides the latency of each operation by time-multiplexing operations of different threads in the datapath. This paper proposes a model to unify multithreading and elasticity. A new multithreaded elastic control protocol is introduced supported by low-cost elastic buffers that minimize the storage requirements without sacrificing performance. To enable the synthesis of multithreaded elastic architectures, new hardware primitives are proposed and utilized in two circuit examples to prove the applicability of the proposed approach.