1,221 research outputs found
An investigation into ageing-resilient processor design
No full textMicroprocessors offer the ability for fast and reliable processing and are indispensable in many general and specific computing systems in different disciplines. In the past decades, CMOS technology size has progressively decreased, which has resulted in devices with smaller areas and lower power consumptions. However, side effects like ageing become more critical at smaller technology sizes, and this bottleneck challenges further improvements in CMOS technology. The main challenge of advanced technologies is at the physical level of the CMOS device, in which the device-level response time degrades over time due to higher-level stress (e.g. workload from a software).Advanced materials that cope with ageing effects could take years to be developed; therefore, this thesis focuses on the stress that is propagated from software-level and explores techniques to mitigate the ageing behaviour by reducing stress from its source. The first part of the thesis targets single-core processors. We present a novel technique to mitigate the bias temperature instability (BTI) ageing effects on microprocessors.After intensive analysis of ageing and its sources from the program level to the device level, we found that an application may stress the critical paths of a circuit in a way that may have half of the nodes always negative BTI stressed, while the second half are positive BTI stressed. To mitigate this behaviour, we propose an application-level solution to reverse the stress and put the processor nodes into a relaxed mode.In the second part of the thesis, we investigate how multi-core processors could be used to mitigate BTI ageing effects by using the fact that idleness is adverse to a processor core at high temperatures. We show that it is necessary to run an anti-ageing program on the idle core in order to relax the stress or proactively avoid the stress generated by a high-level application by analysing the workload and develop a learning model to estimate the stress and its distribution on the multi-core processor. Subsequently, this model is used in a frequency regulator to dynamically adjust the frequencies of the core based on the estimated stress. Results show that by applying the proposed techniques,the ageing stress could be reduced by a half
Bulk-wave ultrasonic propagation imagers
No full textLaser-based ultrasound systems are described that utilize the ultrasonic bulk-wave sensing to detect the damages and flaws in the aerospace structures. These systems apply pulse-echo or through transmission methods to detect longitudinal through-the-thickness bulk-waves. These thermoelastic waves are generated using Q-switched laser and non-contact sensing is performed using a laser Doppler vibrometer (LDV). Laser-based raster scanning is performed by either two-axis translation stage for linear-scanning or galvanometer-based laser mirror scanner for angular-scanning. In all ultrasonic propagation imagers, the ultrasonic data is captured and processed in real-time and the ultrasonic propagation can be visualized during scanning. The scanning speed can go up to 1.8 kHz for two-axis linear translation stage based B-UPIs and 10 kHz for galvanometer-based laser mirror scanners. In contrast with the other available ultrasound systems, these systems have the advantage of high-speed, non-contact, real-time, and non-destructive inspection. In this paper, the description of all bulk-wave ultrasonic imagers (B-UPIs) are presented and their advantages are discussed. Experiments are performed with these system on various structures to proof the integrity of their results. The C-scan results produced from non-dispersive, through-the-thickness, bulk-wave detection show good agreement in detection of structural variances and damage location in all inspected structures. These results show that bulk-wave UPIs can be used for in-situ NDE of engineering structures
An Application-Specific NBTI Ageing Analysis Method
No full textThere is growing concern about time-dependentperformance variations of CMOS devices due to ageing-induceddelay degradation. One of the main causes of ageing is NegativeBias Temperature Instability (NBTI). Existing models whichpredict the impact of NBTI on overall system performanceassume a generic switching activity of input signals of 50 percent.Such an assumption can cause misleading predictions abouthow a circuit’s performance will degrade over time and moreimportantly which parts of the system will be most affected. Thiswork develops a novel NBTI ageing analysis which is based onaccurate calculations of the switching activity for applicationspecificsystems. The proposed method is employed to predictthe ageing of an ARM processor synthesised to 90nm technology.Our results show the proposed ageing analysis techniques cansignificantly reduce prediction errors (e.g. 39% for one of thecritical paths) compared to the generic models, it can also identifymore accurately the parts of the system which are most vulnerableto ageing
BTI mitigation by anti-ageing software patterns
No full textThis paper presents a time-redundant technique to mitigate Negative and Positive Bias Temperature Instability (NBTI/PBTI) ageing effects on the functional units of a processor. We have analysed the sources and effects of ageing from the device level to the Instruction Set Architecture (ISA) level, and have found that an application may stress the critical paths in such a way that the circuit has half of its nodes always NBTI-stressed. To mitigate this behaviour, we propose an application-level solution to balance the stress and put the timing-critical gates of the critical path into a relaxed (balanced) mode. The results show that the lifetime of the system can be doubled by applying balanced stress patterns at the software level during the idle time of a processor system
Static Aging Analysis Using 3-Dimensional Delay Library
No full textThe growing concern about time-dependent performance variations of CMOS devices due to aging-induced delay degradation has increased with shrinking technology dimensions of the devices . One of the main causes of aging is Negative Bias Temperature Instability (NBTI). Modeling NBTI-induced delay at gate level depends on the real stress activity of gate inputs which are related to the workload applied from the higher level of abstraction (e.g. Application). Having estimated values about the degradation delays can make design stage to consider this issue as a design constrain and even to precisely allocate the online aging sensors. this paper propose a method to include the stress probability within technology library as three dimensional look-up tables for Static Timing Analysis(STA) process of the design as an approach named Static Aging Analysis(SAA). the purpose of this approach is instead of estimating only the timing delay at time zero, estimating NBTI-induced delays for predefined lifetime of the product
Learning-based BTI stress estimation and mitigation in multi-core processor systems
No full textWith the increasing demand of designing a reliable processing devices, the issue of CMOS ageing is jeopardising the industry of digital devices. Many studies has been cover this area for modelling the ageing behaviour at the device level or developing ageing sensors for on-line delay detection at the system level. However, we are presenting a method to estimate the ageing stresses (e.g. Temperature, Ageing Stress Activity) rather than the modelling ageing (performance degradation) itself. The purpose for estimating the ageing stress is to optimise the system utilisation with the minimisation of ageing stress. In multicore processors, the existence of more than one source of ageing stress is higher than single core processor but the optimisation space is higher as well along with the temperature and power optimisation. In this paper, we have modelled the ageing stress from the application level using machine learning techniques to train data extracted from high level workloads ( e.g. parsec and splash2 benchmarks) on four cores processor from Xeon. The ageing stress model is able to estimate the ageing stress with 0.1% error and is able to proactively reduce the ageing stress by 50%
Aging Mitigation Techniques for Microprocessors Using Anti-aging Software
No full textIn this chapter, we will aim to reverse the aging stress on the functional units of the processor by applying high-level workloads as anti-aging patterns into the stressed component. We present a time-redundant technique to mitigate negative and positive bias temperature instability (NBTI/PBTI) aging effects on the combinational units of a processor. We have analysed the sources and effects of aging from the device level to the instruction set architecture (ISA) level and have found that an application may stress the critical paths in such a way that the combinational circuit has half of its nodes always NBTI-stressed. To mitigate this behaviour, we propose an application-level solution to balance the stress and put the timing-critical gates of the critical path into a relaxed (balanced) mode. The results show that the lifetime of the system can be extended by applying balanced stress patterns at a higher level of abstraction and during the idle time of a processor system
Evaluating Depression and Stress Among Young Adults Using DASS-21: Towards Personalized Intervention Strategies
No full textDepression, anxiety, and stress are commonly studied in the elderly, often manifesting as a loss of interest in previously enjoyed activities, disrupted sleep patterns, and other emotional or behavioral changes. However, with rapid technological advancements, young adults particularly those between the ages of 20 and 40 are emerging as a highly vulnerable group. This demographic faces a unique psychological burden, as they attempt to navigate the cultural and generational gap between two vastly different worlds: an older generation that often resists or struggles to adapt to revolutionary technologies, and a younger generation having a grip on modern technology. This generational divide can create a sense of isolation and pressure for young adults especially those people living in developing countries where open conversations about mental health still remain stigmatized and difficult to initiate. This research aims to develop a mental health app that can evaluate depression, and stress among young adults using the DASS-21 self-assessment test and suggest a personalized intervention keeping in view the level and severity of depression and stress. For personalized interventions, upper confidence bound algorithm is used to maintain a balance between exploration and exploitation. Agent's performance and effectiveness of intervention is evaluated by a post-test
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