Test Strategies for Low Power Devices

Ultra low-power devices are being developed for embedded applications in bio-medical electronics, wireless sensor networks, environment monitoring and protection, etc. The testing of these low-cost, low-power devices is a daunting task. Depending on the target application, there are stringent guidelines on the number of defective parts per million shipped devices. At the same time, since such devices are cost-sensitive, test cost is a major consideration. Since system-level power-management techniques are employed in these devices, test generation must be power-management-aware to avoid stressing the power distribution infrastructure in the test mode. Structural test techniques such as scan test, with or without compression, can result in excessive heat dissipation during testing and damage the package. False failures may result due to the electrical and thermal stressing of the device in the test mode of operation, leading to yield loss. This paper considers different aspects of testing low-power devices and some new techniques to address these problems.Design, Automation and Test in Europe (DATE \u2708), 10-14 March 2008, Munich, German

Infrastructures and Algorithms for Testable and Dependable Systems-on-a-Chip

Every new node of semiconductor technologies provides further miniaturization and higher performances, increasing the number of advanced functions that electronic products can offer. Silicon area is now so cheap that industries can integrate in a single chip usually referred to as System-on-Chip (SoC), all the components and functions that historically were placed on a hardware board. Although adding such advanced functionality can benefit users, the manufacturing process is becoming finer and denser, making chips more susceptible to defects. Today’s very deep-submicron semiconductor technologies (0.13 micron and below) have reached susceptibility levels that put conventional semiconductor manufacturing at an impasse. Being able to rapidly develop, manufacture, test, diagnose and verify such complex new chips and products is crucial for the continued success of our economy at-large. This trend is expected to continue at least for the next ten years making possible the design and production of 100 million transistor chips. To speed up the research, the National Technology Roadmap for Semiconductors identified in 1997 a number of major hurdles to be overcome. Some of these hurdles are related to test and dependability. Test is one of the most critical tasks in the semiconductor production process where Integrated Circuits (ICs) are tested several times starting from the wafer probing to the end of production test. Test is not only necessary to assure fault free devices but it also plays a key role in analyzing defects in the manufacturing process. This last point has high relevance since increasing time-to-market pressure on semiconductor fabrication often forces foundries to start volume production on a given semiconductor technology node before reaching the defect densities, and hence yield levels, traditionally obtained at that stage. The feedback derived from test is the only way to analyze and isolate many of the defects in today’s processes and to increase process’s yield. With the increasing need of high quality electronic products, at each new physical assembly level, such as board and system assembly, test is used for debugging, diagnosing and repairing the sub-assemblies in their new environment. Similarly, the increasing reliability, availability and serviceability requirements, lead the users of high-end products performing periodic tests in the field throughout the full life cycle. To allow advancements in each one of the above scaling trends, fundamental changes are expected to emerge in different Integrated Circuits (ICs) realization disciplines such as IC design, packaging and silicon process. These changes have a direct impact on test methods, tools and equipment. Conventional test equipment and methodologies will be inadequate to assure high quality levels. On chip specialized block dedicated to test, usually referred to as Infrastructure IP (Intellectual Property), need to be developed and included in the new complex designs to assure that new chips will be adequately tested, diagnosed, measured, debugged and even sometimes repaired. In this thesis, some of the scaling trends in designing new complex SoCs will be analyzed one at a time, observing their implications on test and identifying the key hurdles/challenges to be addressed. The goal of the remaining of the thesis is the presentation of possible solutions. It is not sufficient to address just one of the challenges; all must be met at the same time to fulfill the market requirements

Towards trustworthy computing on untrustworthy hardware

Historically, hardware was thought to be inherently secure and trusted due to its obscurity and the isolated nature of its design and manufacturing. In the last two decades, however, hardware trust and security have emerged as pressing issues. Modern day hardware is surrounded by threats manifested mainly in undesired modifications by untrusted parties in its supply chain, unauthorized and pirated selling, injected faults, and system and microarchitectural level attacks. These threats, if realized, are expected to push hardware to abnormal and unexpected behaviour causing real-life damage and significantly undermining our trust in the electronic and computing systems we use in our daily lives and in safety critical applications. A large number of detective and preventive countermeasures have been proposed in literature. It is a fact, however, that our knowledge of potential consequences to real-life threats to hardware trust is lacking given the limited number of real-life reports and the plethora of ways in which hardware trust could be undermined. With this in mind, run-time monitoring of hardware combined with active mitigation of attacks, referred to as trustworthy computing on untrustworthy hardware, is proposed as the last line of defence. This last line of defence allows us to face the issue of live hardware mistrust rather than turning a blind eye to it or being helpless once it occurs. This thesis proposes three different frameworks towards trustworthy computing on untrustworthy hardware. The presented frameworks are adaptable to different applications, independent of the design of the monitored elements, based on autonomous security elements, and are computationally lightweight. The first framework is concerned with explicit violations and breaches of trust at run-time, with an untrustworthy on-chip communication interconnect presented as a potential offender. The framework is based on the guiding principles of component guarding, data tagging, and event verification. The second framework targets hardware elements with inherently variable and unpredictable operational latency and proposes a machine-learning based characterization of these latencies to infer undesired latency extensions or denial of service attacks. The framework is implemented on a DDR3 DRAM after showing its vulnerability to obscured latency extension attacks. The third framework studies the possibility of the deployment of untrustworthy hardware elements in the analog front end, and the consequent integrity issues that might arise at the analog-digital boundary of system on chips. The framework uses machine learning methods and the unique temporal and arithmetic features of signals at this boundary to monitor their integrity and assess their trust level

Integrating simultaneous bi-direction signalling in the test fabric of 3D stacked integrated circuits.

Jennions, Ian K. - Associate SupervisorThe world has seen significant advancements in electronic devices’ capabilities, most notably the ability to embed ultra-large-scale functionalities in lightweight, area and power-efficient devices. There has been an enormous push towards quality and reliability in consumer electronics that have become an indispensable part of human life. Consequently, the tests conducted on these devices at the final stages before these are shipped out to the customers have a very high significance in the research community. However, researchers have always struggled to find a balance between the test time (hence the test cost) and the test overheads; unfortunately, these two are inversely proportional. On the other hand, the ever-increasing demand for more powerful and compact devices is now facing a new challenge. Historically, with the advancements in manufacturing technology, electronic devices witnessed miniaturizing at an exponential pace, as predicted by Moore’s law. However, further geometric or effective 2D scaling seems complicated due to performance and power concerns with smaller technology nodes. One promising way forward is by forming 3D Stacked Integrated Circuits (SICs), in which the individual dies are stacked vertically and interconnected using Through Silicon Vias (TSVs) before being packaged as a single chip. This allows more functionality to be embedded with a reduced footprint and addresses another critical problem being observed in 2D designs: increasingly long interconnects and latency issues. However, as more and more functionality is embedded into a small area, it becomes increasingly challenging to access the internal states (to observe or control) after the device is fabricated, which is essential for testing. This access is restricted by the limited number of Chip Terminals (IC pins and the vertical Through Silicon Vias) that a chip could be fitted with, the power consumption concerns, and the chip area overheads that could be allocated for testing. This research investigates Simultaneous Bi-Directional Signaling (SBS) for use in Test Access Mechanism (TAM) designs in 3D SICs. SBS enables chip terminals to simultaneously send and receive test vectors on a single Chip Terminal (CT), effectively doubling the per-pin efficiency, which could be translated into additional test channels for test time reduction or Chip Terminal reduction for resource efficiency. The research shows that SBS-based test access methods have significant potential in reducing test times and/or test resources compared to traditional approaches, thereby opening up new avenues towards cost-effectiveness and reliability of future electronics.PhD in Manufacturin

Improving Reusability in SoC Project Verification Flow

This main target of the thesis is to increase the level of reuse done in SoC verification projects. The verification takes the biggest amount of time in the project duration. This thesis contains 3 main parts. The first one introduces the reuse in SoC and explains its different dimensions as a literature study. This work is done as a background for the next two phases. During the second part of this work, a practical example for verification reuse was implemented as a part of a SoC project. The reuse was applied vertically, where an IP-level testbench was altered to become reusable, then it was reused in a subsystem-level testbench. Additionally, analysis was done in order to know how much effort was reused in the project. Results show that 85% of the code was saved when the reuse was applied. Regarding the third part of the thesis, several interviews were conducted with SoC verification experts who work at Nokia with a range of experience in the field from 7 to 20 years. These interviews were done in order to collect some information about how to improve the reusability in SoC project verification flow. The point from these interviews is to get knowledge from hands-on-experience. The interviewees agreed on the importance for applying the reuse in every verification project from the beginning of the project. They also agreed on maintaining the hierarchical level of reuse, which means IP-level TB would be a sub-environment of subsystem-level TB and subsystem-level is a sub-environment of SoC-level TB. Moreover, some ideas about the future work are introduced here. Those are proposed according to the knowledge gained from the research and from the interviews with the experts

Network-on-Chip

Addresses the Challenges Associated with System-on-Chip Integration Network-on-Chip: The Next Generation of System-on-Chip Integration examines the current issues restricting chip-on-chip communication efficiency, and explores Network-on-chip (NoC), a promising alternative that equips designers with the capability to produce a scalable, reusable, and high-performance communication backbone by allowing for the integration of a large number of cores on a single system-on-chip (SoC). This book provides a basic overview of topics associated with NoC-based design: communication infrastructure design, communication methodology, evaluation framework, and mapping of applications onto NoC. It details the design and evaluation of different proposed NoC structures, low-power techniques, signal integrity and reliability issues, application mapping, testing, and future trends. Utilizing examples of chips that have been implemented in industry and academia, this text presents the full architectural design of components verified through implementation in industrial CAD tools. It describes NoC research and developments, incorporates theoretical proofs strengthening the analysis procedures, and includes algorithms used in NoC design and synthesis. In addition, it considers other upcoming NoC issues, such as low-power NoC design, signal integrity issues, NoC testing, reconfiguration, synthesis, and 3-D NoC design. This text comprises 12 chapters and covers: The evolution of NoC from SoC—its research and developmental challenges NoC protocols, elaborating flow control, available network topologies, routing mechanisms, fault tolerance, quality-of-service support, and the design of network interfaces The router design strategies followed in NoCs The evaluation mechanism of NoC architectures The application mapping strategies followed in NoCs Low-power design techniques specifically followed in NoCs The signal integrity and reliability issues of NoC The details of NoC testing strategies reported so far The problem of synthesizing application-specific NoCs Reconfigurable NoC design issues Direction of future research and development in the field of NoC Network-on-Chip: The Next Generation of System-on-Chip Integration covers the basic topics, technology, and future trends relevant to NoC-based design, and can be used by engineers, students, and researchers and other industry professionals interested in computer architecture, embedded systems, and parallel/distributed systems

Optimierung der Energie und Power getriebenen Architekturexploration für Multicore und heterogenes System on Chip

The contribution of this work builds on top of the established virtual prototype platforms to improve both SoC design quality and productivity. Initially, an automatic system-level power estimation framework was developed to address the critical issue of early power estimation in SoC design. The estimation framework models the static and dynamic power consumption of the hardware components. These models are created from the normalized values of the basic design components of SoC, obtained through one-time power simulation of RTL hardware models. The framework allows dynamic technology node reconfiguration for power estimation models. Its instantaneous power reporting aids the detection of possible hotspot early into the design process. Adding this additional data in conjunction with a steadily growing design space of complex heterogeneous SoC, finding the right parameter configuration is a challenging and laborious task for a system-level designer. This work addresses this bottleneck by optimizing the design space exploration (DSE) process for MPSoC design. An automatic DSE framework for virtual platforms (VPs) was developed which is flexible and allows the selection optimal parameter configuration without pre-existing knowledge. To reduce exploration time, the framework is equipped with several multi-objective optimization techniques based on simulated annealing and a genetic algorithm. Lastly, to aid HW/SW partitioning at system-level, a flexible and automated workflow (SW2TLM) is presented. It allows the designer to explore various possible partitioning scenarios without going into depth of the hardware architecture complexity and software integration. The framework generates system-level hardware accelerators from corresponding functionality encoded in the software code and integrates them into the VP. Power consumption and time speedups of acceleration is reported to the designer, which further increases the quality and productivity of the development process towards the final architecture. The presented tools are evaluated using a state-of-the-art VP for a range of single and multi-core applications. Viewing the energy delay product, a reduction in exploration time was recorded at approximately 62% (worst case), maintaining optimal parameter accuracy of 90% compared to previous techniques. While the SW2TLM further increases the exploration versatility by combining modern high-level synthesis with system-level architectural exploration.Der Beitrag dieser Arbeit baut auf dem etablierten Konzept der virtuellen Prototyp (VP) Plattformen auf, um die Qualität und die Produktivität des Entwurfsprozesses zu verbessern. Zunächst wurde ein automatisches System-Level-Framework entwickelt, um Verlustleistungsabschätzung für SoC-Designs in einer deutlich früheren Entwicklungsphase zu ermöglichen. Hierfür werden statischen und dynamischen Energieverbrauchsanteile individueller Hardwareelemente durch ein abstraktes Modell ausgedrückt. Das Framework ermöglicht eine dynamische Anpassung des Technologieknotens sowie die Integration neuer Leistungsmodelle für Drittanbieterkomponenten. Die kontinuierliche Erfassung der Energieverbrauchseigenschaften und ihre grafische Darstellung Benutzeroberfläche unterstützt zusätzlich die frühzeitige Identifikation möglicher Hotspots. Durch die Bereitstellung zusätzlicher Daten, in Verbindung mit einem stetig wachsenden Entwurfsraum komplexer SoCs, ist die Identifikation der richtigen Parameterkonfiguration eine zeitintensive Aufgabe. Die vorgelegten Konzepte erlauben eine gesteigerte Automatisierung des Explorationsprozesses. Techniken der mehrdimensionalen Optimierung, basierend auf Simulated Annealing und genetischer Algorithmen erlauben die Identifikation von geeigneten Konfigurationen ohne vorheriges Wissen oder Erfahrungswerte Schließlich wurde zur Unterstützung der HW/SW -Partitionierung auf System-Ebene ein flexibler und automatisierter Workflow entwickelt. Er ermöglicht es dem Designer verschiedene mögliche Partitionierungsszenarien zu untersuchen, ohne sich in die Komplexität der Hardwarearchitektur und der Softwareintegration zu vertiefen. Das Framework erzeugt abstrakte Beschleunigermodelle aus entsprechenden Softwarefunktionen und integriert sie nahtlos in den ausführbare VP. Detaillierte Daten zum Energieverbrauch, Beschleunigungsfaktor und Kommunikationsoverhead der Partitionierung werden erfasst und dem Designer zur Verfügung gestellt, was die Qualität und Produktivität des weiter erhöht. Die vorgestellten Tools werden mit einer modernen VP für verschiedene SW-Anwendungen evaluiert. Bei Betrachtung des Energieverzögerungsprodukts wurde eine Verringerung der Explorationszeit um mehr als 62% bei 90% Parametergenauigkeit festgestell. Darauf aufbauend, erleichtert die automatisierte Untersuchung verschiedener HW/SW Partitionierungen die Entwicklung heterogener Architekturen durch die Kombination moderner HLS mit Architektur-Exploration auf der Systemebene