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Emerging embedded systems, such as autonomous robots/vehicles, demand a new system-on-a-chip (SoC) that is ultra-low power (mW or even sub-mW level) but highly robust. Such an SoC typically integrates heterogeneous building blocks for supporting a range of features, each ideally operating in an independent voltage and frequency (V/F) domain [1]. In such an architecture, a network-on-chip (NoC) has played a key role to enable high-speed and energy-efficient networking. However, it is increasingly challenging to meet a robustness target since each V/F domain uses a significantly different voltage, e.g., from nominal 1V to near-threshold voltage (NTV), and clock frequency, e.g., from hundreds of MHz to sub-MHz. Furthermore, any two clocks may have uncertain and time-varying phase and frequency relationships. These properties significantly worsen robustness, particularly metastability, in an NoC.
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MPAM: Reliable, Low-Latency, Near-Threshold-Voltage Multi-Voltage/Frequency-Domain Network-on-Chip with Metastability Risk Prediction and Mitigation
Emerging applications like a drone and an autonomous vehicle require system-on-a-chips (SoCs) with high reliability, e.g., the mean-time-between-failure (MTBF) needs to be over tens of thousands of hours [1]. Meanwhile, as these applications require increasingly higher performance and energy efficiency, a multi-core architecture is often desirable. Here, each core operates in an independent voltage/frequency (V/F) domain, ideally from the near-threshold voltage (NTV) to super-threshold, while communicating with one another via a network-on-chip (NoC) [2]. However, this makes it challenging to ensure robustness in clock domain crossing against metastability. Metastability becomes even more critical to NTV circuits since metastability resolution time constant T grows super-linearly with voltage scaling [3]. Conventionally, an NoC uses multi-stage (4 stages in [4]) synchronizers to improve MTBF, but they increase latency and cannot completely eliminate metastability. Recently, [5] proposed a novel NTV flip-flop, which has a lower probability of having metastability. Another recent work [6] proposed to detect the necessary condition of metastability and mitigate it by modulating the RX clock and also requesting retransmission to guarantee data correctness. However, as it detects a necessary condition, not actual metastability, it tends to overly request retransmission, hurting latency, throughput, and energy efficiency.
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- Award ID(s):
- 1919147
- PAR ID:
- 10342207
- Date Published:
- Journal Name:
- 2022 IEEE Custom Integrated Circuits Conference (CICC)
- Page Range / eLocation ID:
- 1 to 2
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/CICC53496.2022.9772849
