S. Hamdioui
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287 records found
1
Bridging the Speed-Accuracy Gap
Layout-Aware Pre-Silicon Side-Channel Analysis
Power side-channel attacks pose a serious threat to cryptographic hardware implementations. To avoid deploying insecure implementations, it is essential to perform side-channel leakage assessments at the pre-silicon stage. Register Transfer Level (RTL)-level or gate-level power traces-generated, for example using SpyGlass, can be produced very efficiently but suffer from limited accuracy. In contrast, post-layout simulations provide a much higher accuracy but are prohibitively time-consuming. In this work, we propose a hybrid approach that extracts layout information, including timing and parasitic effects, and augments the gate-level netlist with this data. This approach enables fast pre-silicon power trace generation that accurately embeds post-layout parasitics. Our results show that power traces generated from gate-level and transistor-level simulations, both augmented with layout information, perform similarly in key-ranking anlysis and have a low Euclidean distance, while the gate-level simulations are 19 x-125 x faster to generate.
Multi-Partner Project
Efficient Deep Learning Platforms for Next-Generation Embedded Edge-AI Systems
Resistive random-access memory (RRAM)-based computation-in-memory (CIM) architectures offer a promising solution to meet the stringent energy efficiency demands of executing artificial intelligence (AI) algorithms directly on edge devices. However, these architectures suffer from the read-disturb problem, which can lead to accumulated computational errors over time. To maintain the required level of computational accuracy, conventional approaches rely on a static reprogramming process after a predefined number of read cycles, necessitating large counters and resulting in inefficiencies. This paper presents experimental results using real RRAM devices to analyze the read-disturb effect and builds on these insights to propose a circuit-level detection methodology for real-time monitoring of conductance drifts. The proposed method initiates reprogramming only when the device drift exceeds a defined threshold and reprogramming is actually needed. Additionally, an analytical method is developed to determine the minimum conductance state ratio needed to meet reliable detection criteria. Based on this foundation, the proposed detection technique is further optimized for dynamic identification of read-disturb effects. Experiment-augmented SPICE simulation results, using a calibrated model implemented in TSMC 40 nm CMOS technology, validate the functionality and effectiveness of the proposed detection approach. These results demonstrate its potential to improve both the reliability and efficiency of RRAM-based CIM architectures that provide up to a 4x improvement in energy-efficiency compared to traditional periodic reprogramming methods.
CIM-FI
A HW-Aware Fault Injection Framework for Digital Compute-In-Memory DNN Accelerators
Although offering great potential for energy-efficient edge-AI, memristor-based CIM accelerators are severely hindered by IR drop induced errors. To tackle this, we propose a low-cost mitigation technique by first quantifying the impact of IR drop on the accuracy. Then, a mitigation strategy is developed to compensate for IR drop-induced inference accuracy reduction by combining an optimized mapping scheme with a fine-tuned calibration of the ADC. Results show the proposed solution can effectively mitigate IR drop with a negligible overhead.
Theoretically speaking, Majority logic, originally proposed in the ^{\prime }70s, enables more compact and efficient arithmetic implementations than the conventional Boolean counterpart. Nonetheless, CMOS technology based Majority logic realizations remain challenging, as standard transistor-based approaches are unable to directly exhibit majority behavior. However, recent exploration on beyond CMOS technologies created a resurgence of the interest in majority logic. In this work, we propose and analyze a novel approach towards the 3-input Majority gate (MAJ3) implementation by means of piezoelectric materials. By leveraging their intrinsic electromechanical properties, we convert the digital input signals into mechanical deformations, which are accumulated in a transfer layer. Subsequently, we transform the combined deformation back to the electric domain with a piezoelectronics element properly designed to perform majority functionality. We first present the underlying principles behind our proposal with a short introduction on majority logic, piezoelectronics, and the utilized simulation framework. Afterwards we introduce the proposed piezoelectric 3-input Majority gate (piezo-MAJ3) and strategies for optimizing its behavior and performance. We also detail the material parameters and structural design impact on device performance by utilizing both analytical discussion and physics-based simulations. Finally, we shortly highlight how our proposal can be directly integrated into CMOS circuits and compare the piezo-MAJ3 potential cost and performance with the ones of state of the art implementations. Our results indicate that when compared with its CMOS counterpart, the piezo-MAJ3 gate requires half the area, it is 7x faster, while reducing with 44% the energy consumption.
SWEET-DREAM
Side-Channel Weakness Evaluation and Enhanced Mitigation for DREAM-CIM
X-Sim
An Accurate and Scalable Simulator for Memristive Computing-in-Memory Accelerators
Computing-in-Memory (CIM) architectures using memristive crossbar arrays enable energy-efficient AI acceleration. Analog non-idealities, such as IR drop and nonlinearity, impose design constraints that existing simulators cannot capture and thus explore effectively. Current approaches sacrifice either modeling accuracy or simulation speed, preventing systematic design space exploration. In this paper we propose X-Sim, a crossbar simulator that resolves this trade-off through a modular architecture. Our approach decouples device physics from circuit analysis using a fixed-point scheme, avoiding expensive Jacobian computations while preserving device fidelity. X-Sim delivers SPICE-level accuracy (< 1% error) with up to 200× speedup over physics-based simulators. This enables quick and systematic design space exploration across thousands of configurations, guiding reliable system design. X-Sim will be released as open source.
Memristor-based neural network accelerators for space applications
Enhancing performance with temporal averaging and SIRENs
Multi-Partner Project
Scalable, Ferroelectric-based Accelerators for Energy Efficient Edge AI (Ferro4EdgeAI)
The Computing-In-Memory (CIM) paradigm offers a promising solution to the memory-wall bottleneck that limits conventional Von Neumann architectures. By performing data processing at the same physical location where the data are stored, CIM-based architectures minimize costly data movement and drastically improve energy efficiency. When implemented with Ferroelectric Field Effect Transistors (FeFETs), additional advantages from the non-volatility, fast switching, and low operating voltage of FeFETs are added. However, the widespread adoption of FeFETs is limited by their poor endurance, which is overcome by a Back End of the Line (BEoL) integration of FeFET-2, where a ferroelectric capacitor (FeCAP) is wired to the gate of a CMOS transistor providing high endurance compatible with low-power edge applications. These properties enable dense, low-power, and high-speed matrix operations essential for AI workloads. As a result, FeFET-2-based CIM accelerators offer a promising solution for energy-efficient, high-performance AI at the edge. The Ferro4EdgeAI project aims to develop an ultra low-power, scalable edge accelerator for AI, targeting a significant gain in energy efficiency with respect to state-of-the-art AI hardware accelerators. To attain this, our project focuses on innovation all along the value chain from materials, physic concepts, device architecture, integration technologies, and accelerators in a holistic design space exploration approach.
Gremlins in the Silicon
Why Faulty Chips are Escaping the Fab and Crashing in the Field
The increasing complexity of semiconductor technologies is exposing limitations in traditional manufacturing test methodologies. Although fault-model-based testing has enabled efficient production screening for decades, growing evidence from advanced logic and memory technologies indicates that many realistic defect mechanisms are insufficiently represented by conventional fault abstractions, leading to test escapes and in-field failures. This paper examines three directions for improving outgoing product quality. First, we discuss the growing mismatch between fault models and actual silicon behavior and emphasize the need for silicon-informed assessment of defect coverage. Second, we investigate timing failures caused by process-variation-induced delay marginalities, which increasingly evade conventional scan-based delay testing. Finally, we present Device-Aware Test (DAT), a defect-centric methodology that derives fault models and test solutions directly from physical defect behavior. Examples from STT-MRAM, RRAM, and FeFET memories demonstrate how DAT enables the detection of realistic defect mechanisms beyond the reach of conventional approaches. Together, these directions support a transition toward defect-aware, data-driven testing for future semiconductor systems.
RRAM-based compute-in-memory (CIM) AI accelerators integrate memory cells with mixed-signal peripherals to enable energy-efficient, low-latency edge computing. These architectures require novel test techniques for unique electrical defects. Current system-level functional tests cannot guarantee defect-free circuits, while accurate circuit-level techniques remain non-scalable to Deep Neural Networks (DNNs). To bridge this gap, we present the first structural test methodology for CIM DNNs, unifying system-level analysis with circuit-level precision. We accurately model RRAM crossbar defects to formulate test patterns, and then propagate results across layers for comprehensive structural testing. Generated test patterns are optimized either for 96% defect coverage or test time reduction by a factor of three while covering all unique defects and maintaining over 73% defect strength coverage.
Spike-based neuromorphic computing
An overview from bio-inspiration to hardware architectures and learning mechanisms
The endeavor to emulate the extraordinary efficiency and adaptability inherent in the human brain via spike-based neuromorphic computing presents significant potential across a diverse array of applications. The attainment of this objective necessitates the translation of biological principles into artificial systems, a task that continues to pose a complex challenge requiring a profound comprehension of the mechanisms by which neural systems produce robust computational outcomes. This tutorial paper provides a comprehensive overview of the foundational concepts and emerging design trends in spike-based neuromorphic computing, covering advances from materials and circuits to hardware architectures and learning mechanisms. It begins with an examination of key aspects of brain biology and their influence on neuromorphic design, followed by a brief discussion of biologically plausible neuron and synapse models. The paper then defines the core principles and defining attributes of neuromorphic computing, highlighting the trade-offs and design choices underlying current implementations. Building on these foundations, it explores the critical properties of neuromorphic systems, surveys a variety of learning algorithms, and reviews hardware-level realizations of bioinspired neurons and synapses. Subsequent sections discuss state-of-the-art spiking neural network architectures, mapping and compilation strategies, and representative application domains. By providing this end-to-end perspective, the article aims to guide the development of future neuromorphic systems that more closely emulate brain efficiency, scalability, and resilience.
The PMP Snapshot Engine
Fast and Fault-Resilient PMP Reconfiguration for RISC-V