Investigation of the power-clock network impact on adiabatic logic

International audienceAdiabatic logic is architecture design style which seems to be a good candidate to reduce the power consumption of digital cores. One key difference is that the power supply is also the clock signal. A lot of work on different adiabatic logic families has been done but the impact of the power supply and the power-clock network still remains to be studied. In this paper, we investigate the power-clock network effect on adiabatic energy dissipation. We derive closed-form analytical formulas to represent the output signal voltage and energy dissipation while taking into account the parasitic impedance of the power-clock network with respect to switching frequency such that adiabatic conditions are still met. Experiments, based on simulation, show that the power-clock network impacts both the energy efficiency of the circuit and its frequency

Shuttle-promoted nano-mechanical current switch

We investigate electron shuttling in three-terminal nanoelectromechanocal device built on a movable metallic rod oscillating between two drains. The device shows a double-well shaped electromechanical potential tunable by a source-drain bias voltage. Four stationary regimes controllable by the bias are found for this device: (i) single stable fixed point, (ii) two stable fixed points, (iii) two limiting cycles, and (iv) single limiting cycle. In the presence of perpendicular magnetic field the Lorentz force makes possible switching from one electromechanical state to another. The mechanism of tunable transitions between various stable regimes based on the interplay between voltage controlled electromechanical instability and magnetically controlled switching is suggested. The switching phenomenon is implemented for achieving both a reliable \emph{active} current switch and sensoring of small variations of magnetic field.Comment: 11 pages, 4 figure

Non-invasive power gating techniques for bursty computation workloads using micro-electro-mechanical relays

PhD ThesisElectrostatically-actuated Micro-Electro-Mechanical/Nano-Electro- Mechanical (MEM/NEM) relays are promising devices overcoming the energy-efficiency limitations of CMOS transistors. Many exploratory research projects are currently under way investigating the mechanical, electrical and logical characteristics of MEM/NEM relays. One particular issue that this work addresses is the need for a scalable and accurate physical model of the MEM/NEM switches that can be plugged into the standard EDA software. The existing models are accurate and detailed but they suffer from the convergence problem. This problem requires finding ad-hoc workarounds and significantly impacts the designer’s productivity. In this thesis we propose a new simplified Verilog-AMS model. To test scalability of the proposed model we cross-checked it against our analysis of a range of benchmark circuits. Results show that, compared to standard models, the proposed model is sufficiently accurate with an average of 6% error and can handle larger designs without divergence. This thesis also investigates the modelling, designing and optimization of various MEM/NEM switches using 3D Finite Element Analysis (FEA) performed by the COMSOL multiphysics simulation tool. An extensive parametric sweep simulation is performed to study the energy-latency trade-offs of MEM/NEM relays. To accurately simulate MEMS/NEMS-based digital circuits, a Verilog-AMS model is proposed based on the evaluated parameters obtained from the multiphysics simulation tool. This allows an accurate calibration of the MEM/NEM relays with a significant reduction in simulation speed compared to that of 3D FEA exercised on COMSOL tool. The effectiveness of two power gating approaches in asynchronous micropipelines is also investigated using MEM/NEM switches and sleep transistors in reducing idle power dissipation with a particular target throughput. Sleep transistors are traditionally used to power gate idle circuits, however, these transistors have fundamental limitations in their effectiveness. Alternatively, MEM/NEM relays with zero leakage current can achieve greater energy savings under a certain data rate and design architecture. An asynchronous FIR filter 4 phase bundled data handshake protocol is presented. Implementation is accomplished in 90nm technology node and simulation exercised at various data rates and design complexities. It was demonstrated that our proposed approach offers 69% energy improvements at a data rate 1KHz compared to 39% of the previous work. The current trends for greater heterogeneity in future Systems-on- Chip (SoC) do not only concern their functionality but also their timing and power aspects. The increasing diversity of timing and power supply conditions, and associated concurrently operating modes, within an SoC calls for more efficient power delivery networks (PDN) for battery operated devices. This is especially important for systems with mixed duty cycling, where some parts are required to work regularly with low-throughput while other parts are activated spontaneously, i.e. in bursts. To improve their reaction time vs energy efficiency, this work proposes to incorporate a power-switching network based on MEM relays to switch the SoC power-performance state (PPS) into an active mode while eliminating the leakage current when it is idle. Results show that even with today0s large and high pull-in voltages, a MEM-relay-based power switching network (PSN) can achieve a 1000x savings in energy compared to its CMOS counterpart for low duty cycle. A simple case of optimising an on-chip charge pump required to switch-on the relay has been investigated and its energy-latency overhead has been evaluated. Heterogeneous many-core systems are increasingly being employed in modern embedded platforms for high throughput at low energy cost considerations. These applications typically exhibit bursty workloads that provide opportunities to minimize system energy. CMOS-based power gating circuitry, typically consisting of sleep transistors, is used as an effective technique for idle energy reduction in such applications. However, these transistors contribute high leakage current when driving large capacitive loads, making effective energy minimization challenging. This thesis proposes a novel MEMS-based idle energy control approach. Core to this approach is an integrated sleep mode management based on the performance-energy states and bursty workloads indicated by the performance counters. A number of PARSEC benchmark applications are used as case studies of bursty workloads, including CPU- and memory- intensive ones. These applications are exercised on an Exynos 5422 heterogeneous many-core platform, engineered with a performance counter facilities, showing 55.5% energy savings compared with an on-demand governor. Furthermore, an extensive trade-off analysis demonstrates the comparative advantages of the MEMS-based controller, including zero-leakage current and non-invasive implementations suitable for commercial off-the-shelf systems.Higher committee of education development in Iraq (HCED

Nanomechanical Resonators: Toward Atomic Scale

The quest for realizing and manipulating ever smaller man-made movable structures and dynamical machines has spurred tremendous endeavors, led to important discoveries, and inspired researchers to venture to new grounds. Scientific feats and technological milestones of miniaturization of mechanical structures have been widely accomplished by advances in machining and sculpturing ever shrinking features out of bulk materials such as silicon. With the flourishing multidisciplinary field of low-dimensional nanomaterials, including one-dimensional (1D) nanowires/nanotubes, and two-dimensional (2D) atomic layers such as graphene/phosphorene, growing interests and sustained efforts have been devoted to creating mechanical devices toward the ultimate limit of miniaturization— genuinely down to the molecular or even atomic scale. These ultrasmall movable structures, particularly nanomechanical resonators that exploit the vibratory motion in these 1D and 2D nano-to-atomic-scale structures, offer exceptional device-level attributes, such as ultralow mass, ultrawide frequency tuning range, broad dynamic range, and ultralow power consumption, thus holding strong promises for both fundamental studies and engineering applications. In this Review, we offer a comprehensive overview and summary of this vibrant field, present the state-of-the-art devices and evaluate their specifications and performance, outline important achievements, and postulate future directions for studying these miniscule yet intriguing molecular-scale machines

Gigahertz Sub-Landauer Momentum Computing

We introduce a fast and highly-efficient physically-realizable bit swap. Employing readily available and scalable Josephson junction microtechnology, the design implements the recently introduced paradigm of momentum computing. Its nanosecond speeds and sub-Landauer thermodynamic efficiency arise from dynamically storing memory in momentum degrees of freedom. As such, during the swap, the microstate distribution is never near equilibrium and the memory-state dynamics fall far outside of stochastic thermodynamics that assumes detailed-balanced Markovian dynamics. The device implements a bit-swap operation -- a fundamental operation necessary to build reversible universal computing. Extensive, physically-calibrated simulations demonstrate that device performance is robust and that momentum computing can support thermodynamically-efficient, high-speed, large-scale general-purpose computing that circumvents Landauer's bound.Comment: 18 pages, 11 figures, 5 appendices; http://csc.ucdavis.edu/~cmg/compmech/pubs/gslmc.ht

Low Loss Plasmon-Assisted Integrated Photonics

Photonic integrated circuits (PICs), semiconductor chips with both photonic and electronic elements, are seeing rapid development and have the potential to transform several industries, such as autonomous driving, computing, telecommunication and quantum networks. However, realization and wide adoption of PICs across the various fields faces a key challenge – soze disparity between electronic (~0.01 um) and photonic components (~100’s of um). Plasmonics, a technology which confines light to the interface of metals and dielectrics, has a potential to address challenges. In particular, it has been shown to led to smaller devices (~10 um or less), enabling higher density optical circuits and devices on-chip. However, the technology is limited by quite extraordinarily high off-state transmission, wherein ~10% of an input signal makes it out of the device. This is simply too high to be practical. This thesis addresses this size disparity, while maintaining high speeds (100’s of GHz), low losses (\u3c 1dB) and high energy efficiency (~ 100 fJ/bit), through the concept of plasmon-assisted devices. The plasmon-assisted design philosophy is based on engaging and disengaging the lossy plasmonic component based on when active modulation is needed. As will be shown, the use of the plasmon-assisted approach generates proposed devices that have the potential to exhibit record performance, significantly elevating the capabilities of integrated photonic devices while greatly reducing the size disparity. For example, the all-oxide modulator can exhibit resistive-capacitive (RC) limited speeds of up to 333 GHz with a sub 0.2 dB insertion loss (IL), while the hybrid polymer-based modulator can exhibit RC limited speeds of 700 GHz but with narrow linewidth. The NOEM based devices can operate with record low energy consumption, down to a few 100 aJ/bit. In addition, this record-breaking performance can be achieved with device that are less than 40 um2 in size

Nanomechanical Resonators: Toward Atomic Scale

The quest for realizing and manipulating ever smaller man-made movable structures and dynamical machines has spurred tremendous endeavors, led to important discoveries, and inspired researchers to venture to previously unexplored grounds. Scientific feats and technological milestones of miniaturization of mechanical structures have been widely accomplished by advances in machining and sculpturing ever shrinking features out of bulk materials such as silicon. With the flourishing multidisciplinary field of low-dimensional nanomaterials, including one-dimensional (1D) nanowires/nanotubes and two-dimensional (2D) atomic layers such as graphene/ phosphorene, growing interests and sustained effort have been devoted to creating mechanical devices toward the ultimate limit of miniaturization--genuinely down to the molecular or even atomic scale. These ultrasmall movable structures, particularly nanomechanical resonators that exploit the vibratory motion in these 1D and 2D nano-to-atomic-scale structures, offer exceptional device-level attributes, such as ultralow mass, ultrawide frequency tuning range, broad dynamic range, and ultralow power consumption, thus holding strong promises for both fundamental studies and engineering applications. In this Review, we offer a comprehensive overview and summary of this vibrant field, present the state-of-the-art devices and evaluate their specifications and performance, outline important achievements, and postulate future directions for studying these miniscule yet intriguing molecular-scale machines