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While 3-D integrated circuits (ICs) offer many advantages over 2-D ICs, thermal management challenges remain unresolved. Thermal through-silicon-vias (TTSVs) are TSVs that facilitate heat transfer across stacked dies without carrying signal and provide a potential thermal management solution to 3-D ICs. However, the use of TTSVs increases the distance between IC blocks and signal delay. The trade-off between temperature and wirelength is difficult to avoid in TTSV-integrated 3-D ICs. Here, we present a hierarchical approach to optimize the floorplan of a 3-D Nehalem-based multicore processor via simulated annealing (SA). Our simulations show that an increase in the TTSV area accompanies a decrease in peak temperature but the wirelength strongly depends on the TTSV placement, which is uniquely optimized for each case of the allowed TTSV area. Compared to the floorplan with a fixed TTSV placement that places TTSV between cores, our algorithm optimally places TTSVs between IC blocks and finds an optimal floorplan with the minimum cost of peak temperature, wirelength, and area at 6% TTSV area overhead. The peak temperature is reduced from 116 °C to 100 °C with only a 3.5% increase in wirelength. Our floorplan optimization method can provide effective thermal management solutions to 3-D ICs. [ABSTRACT FROM AUTHOR]

This paper proposes energy-efficient approximate multipliers based on the Mitchell's log multiplication, optimized for performing inferences on convolutional neural networks (CNN). Various design techniques are applied to the log multiplier, including a fully-parallel LOD, efficient shift amount calculation, and exact zero computation. Additionally, the truncation of the operands is studied to create the customizable log multiplier that further reduces energy consumption. The paper also proposes using the one's complements to handle negative numbers, as an approximation of the two's complements that had been used in the prior works. The viability of the proposed designs is supported by the detailed formal analysis as well as the experimental results on CNNs. The experiments also provide insights into the effect of approximate multiplication in CNNs, identifying the importance of minimizing the range of error.The proposed customizable design at $w$w = 8 saves up to 88 percent energy compared to the exact fixed-point multiplier at 32 bits with just a performance degradation of 0.2 percent for the ImageNet ILSVRC2012 dataset. [ABSTRACT FROM AUTHOR]

3D integration opens up new opportunities for future multiprocessor chips by enabling fast and highly scalable 3D Network-on-Chip (NoC) topologies. However, in an aim to reduce the cost of Through-silicon via (TSV), partially vertically connected NoCs, in which only a few vertical TSV links are available, have been gaining relevance. To reliably route packets under such conditions, we introduce a lightweight, efficient and highly resilient adaptive routing algorithm targeting partially vertically connected 3D-NoCs named First-Last. It requires a very low number of virtual channels (VCs) to achieve deadlock-freedom (2 VCs in the East and North directions and 1 VC in all other directions), and guarantees packet delivery as long as one healthy TSV connecting all layers is available anywhere in the network. An improved version of our algorithm, named Enhanced-First-Last is also introduced and shown to dramatically improve performance under low TSV availability while still using less virtual channels than state-of-the-art algorithms. A comprehensive evaluation of the cost and performance of our algorithms is performed to demonstrate their merits with respects to existing solutions. [ABSTRACT FROM AUTHOR]

In this paper, we propose an energy-efficient reconfigurable platform for in-memory processing based on novel four-terminal spin Hall effect-driven domain wall motion devices that could be employed as both nonvolatile memory cell and in-memory logic unit. The proposed designs lead to unity of memory and logic. The device to system level simulation results show that, with 28% area increase in memory structure, the proposed in-memory processing platform achieves a write energy ~15.6 fJ/bit with 79% reduction compared to that of SOT-MRAM counterpart while keeping the identical 1 ns writing speed. In addition, the proposed in-memory logic scheme improves the operating energy by 61.3%, as compared with the recent nonvolatile in-memory logic designs. An extensive reliability analysis is also performed over the proposed circuits. We employ advanced encryption standard (AES) algorithm as a case study to elucidate the efficiency of the proposed platform at application level. Simulation results exhibit that the proposed platform can show up to 75.7% and 30.4% lower energy consumption compared to CMOS-ASIC and recent pipelined domain wall (DW) AES implementations, respectively. In addition, the AES energy-delay product can show 15.1% and 6.1% improvements compared to the DW-AES and CMOS-ASIC implementations, respectively. [ABSTRACT FROM AUTHOR]

2D-NoCs have been the mainstream approach used to interconnect multi-core systems. 3D-NoCs have emerged to compensate for deficiencies of 2D-NoCs such as long latency and power overhead. A low-latency routing algorithm for 3D-NoC is designed to accommodate high-speed communication between cores. Both simulation and analytical models are applied to estimate the communication latency of NoCs. Generally, simulations are time-consuming and slow down the design process. Analytical models provide, within a fraction of the time, nearly accurate results which can be used by simulation to fine-tune the design. In this paper, a high performance and adaptive routing algorithm has been proposed for partially connected 3D-NoCs. Latency of the routing algorithm under different traffic patterns, different number of elevators and different elevator assignment mechanisms are reported. An analytical model, tailored to the adaptivity of the algorithm and under low traffic scenarios, has been developed and the results have been verified by simulation. According to the results, simulation and analytical results are consistent within a 10 percent margin. [ABSTRACT FROM AUTHOR]

In modern many-core architectures, advanced on-chip networks provide the means of communication for the cores. This greatly complicates the design and verification of the cache coherence protocols deployed by those cores. A common approach to deal with this complexity is to decompose the whole system into the protocol and the network. This decomposition is, however, not always possible. For example, unexpected deadlocks can emerge when a deadlock-free protocol and a deadlock-free network are combined. This paper proposes a compositional methodology: prove properties over a network, prove properties over a protocol, and infer properties over the system as a whole. Our methodology is based on theorems that show that such decomposition is possible by having sufficiently large local buffers at the cores. We apply this methodology to verify several protocols such as MI, MSI, MESI and MEUSI running on top of advanced interconnects with adaptive routing. [ABSTRACT FROM AUTHOR]

The movement toward 3D fabrication coupled with Network-on-Chip (NoC) aims to improve area, performance, power, and scalability of many-core systems. However, reliability issue as a perpetual challenge in advanced silicon technology imperils it. Aging is an emerging reliability concern, which degrades the system's performance and causes timing failure eventually. Bias-Temperature-Instability (BTI) and Hot-Carrier-Injection (HCI) are the dominant aging mechanisms, which escalate in high temperature and stress (i.e., usage). In addition to the intra-layer temperature variations, 3D NoCs experience inter-layer temperature variations, which demand necessary investigations for aging as compared to 2D NoC. In this paper, we propose AROMa, an aging-aware deadlock-free adaptive routing algorithm integrated with a novel online aging monitoring system for 3D NoCs. The monitoring system in AROMa exploits Distributed-Centralized-Aging-Table (D-CAT) to obtain routers’ aging rates for each layer of 3D NoCs periodically. Consequently, AROMa swaps between different k-best source-destination shortest paths periodically to avoid highly aged routers, force them in recovery phase of BTI, and accordingly balance aging in the network. We prove that AROMa is deadlock free. Our extensive experimental analysis using gem5 full system mode for PARSEC and SPLASH-2 benchmark suites concludes that AROMa outperforms state-of-the-art works while improving age imbalance by 70 percent and maximum age by 35 percent in 3D NoC with negligible overheads. [ABSTRACT FROM AUTHOR]

To implement a fuzzy system, the first and the most essential step is to design basic fuzzy modules such as analog min and max circuits. This paper presents efficient minimum and maximum circuits using carbon nanotube FETs (CNTFETs) for nanotechnology-based fuzzy circuits and systems. The proposed approach considerably reduces the design complexity in the fuzzy space. In the proposed design, the chirality of carbon nanotubes is utilized for threshold voltage determination. Extensive simulations conducted using HSPICE and the Stanford CNTFET model at 16 nm feature size demonstrate that the proposed fuzzy logic blocks considerably improve the performance parameters and function much more robustly even in the presence of process variations, as compared to their CNTFET-based counterparts. [ABSTRACT FROM PUBLISHER]

Biased-Temperature-Instability (BTI) aging mechanism reduces Static-Noise-Margin (SNM) of SRAM cells. This leads to a higher Soft-Error-Rate (SER), lower reliability, and lower SRAMs’ stability in FPGAs. SNM partially improves by leveraging the recovery phase of BTI through flipping SRAM content. We propose STABLE, a three-step post-synthesis stress-aware technique, in order to reduce the impact of BTI-induced SNM reduction in FPGA Look-up-Tables (LUTs) using the SAT-based Boolean Matching (BM) algorithm. STABLE partitions Data-Flow-Graph (DFG) of the implemented design into different cones. First, the SAT-based BM algorithm finds a new configuration for each cone while their functionalities are preserved and all SRAMs are flipped. Second, cones that did not pass the first step can benefit from unused SRAMs in their partially-used LUTs for storing the flipped configurations of such LUTs. Finally, flipped configurations of fully-used LUTs are stored in the closest unused LUTs. The main configuration of the implemented FPGA design is swapped by the new flipped configuration, periodically. Our extensive experimental analysis demonstrates 69 and 70 percent on average improvements in the SNM reduction () and the SER increase ( $\Delta SER$), respectively. Since the proposed methodology is deployed after the FPGA placement and routing of the application, the overhead is negligible. [ABSTRACT FROM PUBLISHER]

Fault-tolerant minimal routing algorithms aim at finding a Manhattan path between the source and destination nodes and route around all faulty nodes. Additionally, some non-faulty nodes that are helpless to make up of a fault-tolerant minimal path should also be routed around. How to label such non-faulty nodes efficiently is a major challenge. State-of-the-art solutions could not address it very well. We propose a path-counter method. It can label every node that are helpless to make up of a fault-tolerant minimal path with low time complexity. By counter the number of fault-tolerant minimal paths, it can: support arbitrary fault distribution, check the existence of fault-tolerant minimal paths, not sacrifice any available fault-tolerant minimal paths. [ABSTRACT FROM AUTHOR]

This paper proposes a highly scalable sensor design for late transition detection in FPGA based platforms. Transition delays occur because of aging mechanisms such as Biased Temperature Instability (BTI) and Hot Carrier Injection (HCI). We propose a sensor clock (SCLK) that is a function of minimum slack time of a set of paths selected for age monitoring. There will be one such clock for many sensors as are needed in an entire FPGA. Our proposed sensor architecture makes it possible for a single SCLK to be shared by all sensors. Additionally, the proposed sensor occupies one slice (basic FPGA logic block), which leads to low area, power, and performance overhead. Using Artix-7-based board, experimental results demonstrate that the proposed aging sensor detects aging earlier than existing sensors and provides less power and performance overheads. [ABSTRACT FROM AUTHOR]

Cache coherence plays a major role in manycore systems. The verification of deadlocks is a challenge in particular, because deadlock freedom is an emerging property. Formal methods often decouple verification of the protocol from verification of the communication interconnect. Modern communication fabrics, however, become more advanced and include a network topology, routing, arbitration, synchronization, and more. In this paper, an integrated approach is proposed that allows cross-layer verification of both the cache coherence protocol and the communication fabric all at once. An automated methodology for deriving cross-layer invariants is proposed. These invariants relate the state of the application-layer protocols to en route packets in the communication fabric. Using the invariants, we derive formal proofs of deadlock-freedom for two case studies: a directory-based MI protocol in a 2D mesh, and a ring-based snoopy protocol in a 2D torus. Additionally, we show that our methodology can be used to derive the smallest possible queue sizes that ensure absence of deadlocks. Our methodology is generally applicable and shows promising scalability. [ABSTRACT FROM PUBLISHER]

3D ICs can take advantage of a scalable communication platform, commonly referred to as the Networks-on-Chip (NoC). In the basic form of 3D-NoC, all routers are vertically connected. Partially connected 3D-NoC has emerged because of physical limitations of using vertical links. Routing is of great importance in such partially connected architectures. A high-performance, fault-tolerant and adaptive routing strategy with respect to the communication flow among the cores is crucial while freedom from livelock and deadlock has to be guaranteed. In this paper we introduce a new routing algorithm for partially connected 3D-NoCs. The routing algorithm is adaptive and tolerates the faults on vertical links as compared to the predesigned routing algorithms. Our results show a $40-50\%$ improvement in the fraction of intact inter-level communications when the fault tolerant algorithm is used. This routing algorithm is light-weight and has only one virtual channel along the $Y$ dimension. [ABSTRACT FROM AUTHOR]

Recently, Through-Silicon-Via (TSV) has been more popular to provide faster inter-layer communication in three-dimensional Networks-on-Chip (3D NoCs). However, the area overhead of TSVs reduces wafer utilization and yield which impact design of 3D architectures using a large number of TSVs such as homogeneous 3D NoCs topologies. Also, 3D routers require more memory and thus they are more power hungry than conventional 2D routers. Alternatively, hybrid 3D NoCs combine both the area and performance benefits of 2D and 3D router architectures by using a limited number of TSVs. Existing hybrid architectures suffer from higher packet delays as they do not consider the dynamic communication patterns of different application and their NoC resource usage. We propose a novel algorithm to systematically generate hybrid 3D NoC topologies for a given application such that the vertical connections are minimized while the NoC performance is not sacrificed. The proposed algorithm analyses the target application and generates hybrid architectures by efficiently redistributing the vertical links and buffer spaces based on their utilizations. Furthermore, the algorithm has been evaluated with synthetic and various real-world traffic patterns. Experimental results show that the proposed algorithm generates optimized architectures with lower energy consumption and a significant reduction in packet delay compared to the existing solutions. [ABSTRACT FROM PUBLISHER]

As the number of on-chip processor cores increases, power-efficient solutions are sought for data communication between cores. The Helix-h non-blocking photonic switch is developed to improve physical-layer and network performance parameters for a wide range of silicon nano-photonic multicore interconnection topologies. Traffic benchmarks and practical case studies using a cycle-accurate simulation environment indicate significantly reduced insertion loss providing improved bandwidth density and scalability to manycore plurality. Improvements in system performance parameters are quantified for network bandwidth, transmission efficiency, and latency in popular photonic internconnection topologies, in comparison to previous switch designs. For instance, utilizing the Helix-h switch in a mesh topology, the bandwidth is increased by 112 percent compared to the previously highest performing switch design. Execution time and energy efficiency are improved by up to 92 and 99 percent, respectively, for representative multicore applications. Finally, the technique is generalized to a novel graph-theoretic method for articulating blocking conditions in photonic switches. [ABSTRACT FROM AUTHOR]

TSV-to-TSV coupling is known to be a significant detriment to signal integrity in three-dimensional (3D) IC architectures. Designing a reliable Through-Silicon Via is critical in order to support better performance. This paper explores the challenges brought on by capacitive and inductive TSV-to-TSV coupling in TSV-based 3D ICs. Based on our analyses, we propose two approaches to mitigate these effects. In one approach, a novel coding technique that adjusts the current flow pattern is proposed to mitigate the inductive coupling effects. In another approach an alternative architecture, wrapping around the TSVs, is proposed to greatly reduce the capacitive coupling effect. The efficiency of the proposed coding methods and supporting architectures is demonstrated by comprehensive simulations at both the hardware and system levels. [ABSTRACT FROM AUTHOR]

A 3-D multiple-stacked IC has been proposed to support energy efficiency for data center operations as dynamic RAM (DRAM) scaling improves annually. 3-D multiple-stacked IC is a single package containing multiple dies, stacked together, using through-silicon via (TSV) technology. Despite the advantages of 3-D design, fault occurrence rate increases with feature-size reduction of logic devices, which gets worse for 3-D stacked designs. TSV coupling is one of the main reliability issues for 3-D multiple-stacked IC data TSVs. It has large disruptive effects on signal integrity and transmission delay. In this paper, we first characterize the inductance parasitics in contemporary TSVs, and then we analyze and present a classification for inductive coupling cases. Next, we devise a coding algorithm to mitigate the TSV-to-TSV inductive coupling. The coding method controls the current flow direction in TSVs by adjusting the data bit streams at run time to minimize the inductive coupling effects. After performing formal analyses on the efficiency scalability of devised algorithm, an enhanced approach supporting larger bus sizes is proposed. Our experimental results show that the proposed coding algorithm yields significant improvements, while its hardware-implemented encoder results in tangible latency, power consumption, and area. [ABSTRACT FROM AUTHOR]

Reliability is one of the most challenging problems in the context of three-dimensional network-on-chip (3D NoC) systems. Reliability analysis is prominent for early stages of the manufacturing process in order to prevent costly redesigns of a target system. This article classifies the potential physical faults of a baseline TSV-based 3D NoC architecture by targeting two-dimensional (2D) NoC components and their inter-die connections. In this paper, through-silicon via (TSV) issues, thermal concerns, and single event effect (SEE) are investigated and categorized, in order to propose evaluation metrics for inspecting the resiliency of 3D NoC designs. A reliability analysis for major source of faults is reported in this article separately based on their mean time to failure (MTTF). TSV failure probability induced by inductive and capacitive coupling is also discussed. Finally, the paper provides a formal reliability analysis on the aggregated faults that affect TSV. This formal analysis is critical for estimating the resiliency of different components in order to mitigate the redundancy cost of fault-tolerant design or to examine the efficiency of any proposed fault-tolerant methods for 3D NoC architectures. [ABSTRACT FROM PUBLISHER]