Accurate characterization of radiation-induced soft errors is a critical step toward understanding the impact of these glitches on circuit and system reliability. With process scaling, there has been exponential increase in number of transistors that can be packed on a die which, in turn, results in higher sensitive node count and persistent soft error susceptibilities. In this work, a novel circuit technique employing higher sensitivity toward soft errors is proposed. The circuit makes use of current-starved gates with bias knobs to fine-tune both measurement resolution and strike sensitivity enabling accelerated and efficient induction of errors in a limited-time irradiation test environment. The back-sampling chain (BSC) circuit can measure individual radiation-induced transient pulse with as low amplitude as$0.3\times $VDD while maintaining a high measurement resolution for pulsewidth characterization. The bias knobs allowing tuning of sensitivity and resolution enable, for the first time, a strike pulse waveform reconstruction methodology that can be used to calibrate current pulse models for assessing soft error rate (SER) sensitivity of standard logic gates.

The system-on-chip (SoC) designs for future Internet of Things (IoT) systems, spanning client platforms to cloud datacenters, need to deliver uncompromising and scalable performance with extreme energy efficiency for diverse workloads and applications, while satisfying a wide range of energy budgets, as well as platform cooling and power delivery constraints. Low-latency, burst-mode responsiveness, and scalable high-throughput performance must be delivered on demand for a range of thread-parallel, task-parallel, and data-parallel workloads covering traditional and emerging applications. This article discusses the challenges and opportunities for many-core SoC design in scaled CMOS process operating over a wide voltage-frequency range including near-threshold-voltage (NTV) that can meet the compute demands of the future at scale, flexibly, and efficiently. This article covers: 1) circuit design techniques for NTV cores; 2) mitigation techniques for within-die parameter variations via multivoltage frequency schemes; 3) digital integrated voltage regulators (VRs) for fine-grain and wide-range voltage modulation; and 4) radiation-induced soft error rate (SER) characterization and mitigation techniques to enable reliable operation at NTV. Silicon prototype examples will be used to illustrate the different techniques and highlight future research directions.

A quad-output elastic switched capacitor converter with four cores and per-core digital low dropout regulators (LDOs) is designed in 130nm CMOS. This design routes power on demand by sharing the total switching capacitance network across all the cores and delivering power to each core in a time interleaved manner. As the current demand of a core increases, more switching capacitance and switch area resources are automatically allotted to the core. In case of further power demand, if the power delivery module can no longer allocate further resources, then it autonomously changes the voltage conversion ratio till the demand is met. Measurements reveal 87% peak power efficiency and 2.5× increase in core-frequency range, thus enabling wider dynamic voltage and frequency scaling (DVFS).

This paper presents an overview of methods for combinational, base-two logarithmic approximation using Mitchell's algorithm, piecewise-linear/quadratic error compensation schemes, and direct approximation. Optimization methods are used for computing linear segments for each compensation scheme including Hamming weight minimization and pattern recognition of segment slopes for multiplier-less error compensation. A novel, near-zero-average error quadratic compensation scheme is also presented. A test chip was fabricated in a commercial 130nm technology including fifteen base-two logarithm approximations and each was evaluated for its standalone accuracy, measured energy, delay, and area in order to determine the best classes of approximation for low-energy and high-accuracy operation. A system-level evaluation of these methods was performed using a software model of a keyword detection speech pipeline to predict the impact of inaccurate logarithmic approximation on the detection accuracy of keywords across various noise levels.

Resilient techniques are commonly employed for dynamic and static variation tolerance. In this paper, we present an adaptive clocking technique that achieves 31% throughput increase with 15% energy reduction, and an adaptive interconnect fabric technique that increases bandwidth by 63% with 14.6% energy reduction. We also discuss variations in many-core microprocessors and some techniques to enable a resilient many-core system on a chip.

The minimum supply voltage (Vmin) is explored for sequential logic circuits by statistically simulating the impact of within-die process variations and gate-dielectric soft breakdown on data retention and hold time. As supply voltage (Vcc) scales, statistical circuit simulations demonstrate that hold time increases faster than circuit delay or cycle time, consequently the required number of min-delay buffers increases. For this reason, a new hold-time violation metric defines Vminas the Vccin which the hold time exceeds a target percentage of the cycle time. Simulation results in a 22nm tri-gate CMOS technology indicate a data-retention Vminof 0.61Vnorm and a hold-time Vminof 0.73Vnorm, where Vnormrepresents a normalized voltage for the process technology node. A key insight reveals that upsizing the first clock inverter in the sequential circuit reduces the hold-time Vminby 18% and the overall Vminby 16%.

This session brings together specialists from the DfT, DfY and DfR domains that will address key problems together with their solutions for the 14 nm node and beyond, dealing with extremely complex chips affected by high defect levels, unpredictable and heterogeneous timing behavior, circuit degradation over time, including extreme situations related with the ultimate CMOS nodes, where all processor nodes, routers and links of single-chip massively parallel tera-device processors could comprise timing faults (such as delay faults or clock skews); a large percentage of these parts are affected by catastrophic failures; all parts experience significant performance degradations over time; and new catastrophic failures occur at low MTBF.

Traditional processors are designed to guarantee error-free operation under worst-case (1) device & interconnect parameter variations resulting from less than ideal manufacturing process control; (2) static & erratic defects; (3) operating environments such as temperature excursions and voltage droops; (4) critical path activation and path delay degradations due to multiple inputs switching simultaneously in gates containing transistor stacks, or signal coupling from neighboring lines in interconnect paths; (5) speed degradation over the operating lifetime due to transistor aging under voltage, temperature & current stress; (6) early-life failures due to latent defect accelerations; and (7) soft error due to cosmic rays and alpha particle impacts. The voltage-frequency settings for all processors are set based on these infrequently encountered worst-case considerations, even though under typical conditions voltage can be pushed down further or frequency increased without causing errors for most of the processors, thus limiting both energy efficiency and performance in scaled CMOS technologies.

In this tutorial, a 45nm resilient microprocessor core with error-detection and recovery circuits demonstrates the opportunity for improving performance and energy efficiency by mitigating the impact of dynamic parameter variations. The design methodology describes the additional steps beyond a standard design flow for integrating error-detection and recovery circuits into a microprocessor core. Silicon measurements indicate that the resilient design enables a 41% throughput benefit at iso-energy or a 22% energy reduction at iso-throughput, as compared to a conventional design.

Conventional microprocessors require a clock frequency (F CLK ) guardband to ensure correct functionality during infrequent dynamic operating variations in supply voltage (V CC ), temperature, and transistor aging. Consequently, these inflexible designs cannot exploit opportunities for higher performance by increasing F CLK or lower energy by reducing V CC during favorable operating conditions. This presentation describes a 45nm resilient microprocessor with error-detection and recovery circuits to detect and correct timing errors from dynamic variations to mitigate the F CLK guardband, thus enabling higher performance or lower energy as compared to a conventional design. The microprocessor core supports two distinct error-detection designs and two separate error-recovery techniques, allowing a direct comparison of the relative trade-offs. Silicon measurements demonstrate that resilient circuits enable a 41% throughput gain at equal energy or a 22% energy reduction at equal throughput, as compared to a conventional design when executing a benchmark program with a 10% V CC droop. In addition, the resilient circuits guide an adaptive clock controller that tracks recovery cycles and adapts to persistent variations by changing F CLK . The combination of error-detection and recovery circuits with dynamic adaptation allows the microprocessor to adapt to the operating environment to deliver maximum efficiency. The presentation concludes by discussing the opportunity of applying resilient techniques to enhance the dynamic operating range (i.e., high-performance and low-power modes) for microprocessors.

Three circuit techniques for dynamic variation tolerance are presented: (i) Sensors with adaptive voltage and frequency circuits, (ii) Tunable replica circuits for timing-error prediction with error recovery, and (iii) Embedded error-detection sequential circuits with error recovery. These circuits mitigate the clock frequency guardbands for dynamic variations, thus improving microprocessor performance and energy-efficiency. These circuits are described with a focus on the different trade-offs in guardband reduction and design overhead. Opportunities for CAD to further enhance microprocessor performance and energy efficiency are offered.

Voltage and frequency margins necessary to ensure correct processor operation under dynamic voltage, temperature, and aging variations result in performance and power overheads. Resilient circuit techniques, including embedded error-detection sequentials and tunable replica circuits, allow these margins to be reduced or eliminated, resulting in reliable, energy-efficient operation.

Design of reliable systems meeting stringent quality, reliability, and availability requirements is becoming increasingly difficult in advanced technologies. The current design paradigm, which assumes that no gate or interconnect will ever operate incorrectly within the lifetime of a product, must change to cope with this situation. Future systems must be designed with built-in mechanisms for failure tolerance, prediction, detection and recovery during normal system operation. This tutorial will focus on models and metrics for designing reliable systems, algorithms and tools for modeling and evaluating such systems, will discuss a broad spectrum of techniques for building such systems with support for concurrent error detection, failure prediction, error correction, recovery, and self-repair. Complex interplay between power, performance and reliability requirements in future systems, and associated constraints will also be discussed.

We explore the power benefits of changing a microprocessor path histogram through circuit sizing based on statistical timing analysis and optimization (STAO) versus a deterministic timing approach that uses statistical design to establish a global guardband followed by conventional optimization (SDGG). Using an analytical modeling approach, we quantify the differences in total power between the two approaches while maintaining an equivalent performance distribution. For a relative 1σ random WID stage delay variation of 5% and representative microprocessor critical paths, the analysis indicates that the STAO approach enables ~2% power reduction over the SDGG approach. To achieve a 4% and 6% power reduction through the STAO approach, the process variation needs to increase by a factor of 2x and 4x, respectively.

This paper presents adaptive variation-and-error-resilient agent (AVERA), an approach to address the challenge of designing reliable systems in the presence of soft errors and variations. AVERA extends our previous built-in soft error resilience (BISER) approach by adding additional capabilities to support process variation diagnosis, degradation detection, and system adaptation, besides soft error correction. We also discuss open challenges for building variation-and-error-resilient systems.

Insertion of time-borrowing (TB) flip-flops in multi-cycle repeater-based on-chip interconnects enables significant improvements in mean performance and energy by averaging systematic and random within-die (WID) delay variations across multiple interconnect segments. A statistically-based analytical model is derived to design a TB N-cycle interconnect with optimal delay variation tolerance. The model elucidates the dependency of the transparency window required to achieve data delay averaging on the delay variation mismatch between interconnect segments. Statistical circuit simulations and analyses in a 65nm process technology demonstrate that TB multi-cycle interconnects enable a 4-6% mean maximum clock frequency (FMAX) improvement and a corresponding 10% average energy savings over optimally designed multi-cycle interconnects with conventional master-slave flip-flops. The maximum mean FMAX benefit ranges from 4.0-7.5%, corresponding to approximately a bin-split shift in the FMAX distribution. For 1.41X larger WID delay variations, the maximum mean FMAX gain rises to 5-10%.

As device dimensions continue to scale with every process generation, the impact of variations of all types is becoming more pronounced. Static process variations - due in part to the widening gap between the process dimensions and the wavelength of light used in lithography - are worsening, while dynamic reliability degradation and aging is becoming a severe problem. At the same time, environmental variations in supply voltage, temperature,and noise are also increasing in importance as circuits are packed more tightly on a die. These variations, which ultimately impact the frequency and power consumption of the fabricated design, have traditionally been handled through a combination of circuit design as well as margining of the frequency and voltage for the final product. However, as variations increase and power constraints are tightened, this margining approach is non-optimal. This session will examine how industry designs have accounted for variations - from the design phase to the operation of the system itself, and considers the challenges that lie ahead in testing these variation-aware designs.

Passive shielding has been used to reduce the capacitive coupling effects of adjacent bus lines by inserting passive ground or power lines (shields) between them. Active shielding is another shielding technique in which the shield is allowed to switch depending on the switching pattern of its adjacent bus lines. This paper formally derives the optimal active shielding logic function for minimum power dissipation. It is also shown that this optimal active shielding architecture depends on the ratio of coupling to ground capacitance (/spl gamma/=C/sub c//C/sub g/). Optimal active shielding is shown to provide up to 25% reduction in bus power dissipation compared to conventional passive shielding. A suboptimal active shielding architecture with simpler hardware is also proposed. Theoretically, using the suboptimal shielding architecture leads to less than 6% bus power penalty compared to the optimal active shielding logic circuit. However, due to the simpler shield encoding circuitry, simulation results show that the suboptimal active shielding architecture leads to higher overall energy savings compared to the optimal active shielding architectures.

Die-to-die and within-die variations impact the frequency and power of fabricated dies, affecting functionality, performance, and revenue. Variation-tolerant circuits and post-silicon tuning techniques are important for minimizing the impacts of these variations. This paper describes several circuit techniques that can be employed to ensure efficient circuit operation in the presence of ever-increasing variations.

As technology scales, the shrinking wire width increases the interconnect resistivity, while the decreasing interconnect spacing significantly increases the coupling capacitance. This paper proposes reducing the number of bus lines of the conventional parallel-line bus CB architecture by multiplexing each m-bits onto a single line. This bus architecture, the serial-link bus SLB, transforms an n-bit conventional parallel-line bus into an n/m-line (serial-link) bus. The advantage of serial-link buses is that they have fewer lines, and if the bus width is kept the same, serial- link buses will have larger line width and spacing. Increasing the line width has a twofold reduction effect on the line resistance, as the resistivity of sub-100 nm wires significantly drops as the line width increases. Also, increasing the line width and spacing reduces the coupling capacitance between adjacent lines, but increases the line-to-ground capacitance. Thus, an optimum degree of multiplexing m exists that minimizes the bus energy dissipation and maximizes the bus throughput per-unit area. The optimum degree of multiplexing for maximum throughput-per- unit-area and for minimum energy dissipation for the 25-130 nm technologies was determined in this paper. HSPICE simulations show that; for the same throughput-per-unit-area as conventional parallel-line buses, the serial-link bus architecture reduces the energy dissipation by up to 31.42% for a 64-bit bus implemented in an intermediate metal layer of a 50 nm technology and a reduction of 52.7% is projected for the 25 nm technology.

This paper proposes a bus architecture called skewed repeater bus (SRB) for reducing on-chip interconnect energy in microprocessors. By introducing relative delay between neighboring bus lines, SRB reduces both average and worst-case coupling capacitance between those lines. SRB is compared to previously published techniques like delayed data bus (DDB) and delayed clock bus (DCB). Simulation results in 65-nm process show that bus energy reduction of 18% is achieved when SRB is applied to a real microprocessor example, versus 11% and 7% only for DDB and DCB; respectively.

Parameter variation in scaled technologies beyond 90nm will pose a major challenge for design of future high performance microprocessors. In this paper, we discuss process, voltage and temperature variations; and their impact on circuit and microarchitecture. Possible solutions to reduce the impact of parameter variations and to achieve higher frequency bins are also presented.

We describe various design automation solutions for design migration to a dual-Vt process technology. We include the results of a Lagrangian Relaxation based tool, iSTATS, and a heuristic iterative optimization flow. Joint dual-Vt allocation and sizing reduces total power by 10+% compared with Vt allocation alone, and by 25+% compared with pure sizing methods. The heuristic flow requires 5x larger computation runtime than iSTATS due to its iterative nature.

Article Comparative delay and energy of single edge-triggered & dual edge-triggered pulsed flip-flops for high-performance microprocessors Share on Authors: James Tschanz Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, OR Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, ORView Profile , Siva Narendra Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, OR Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, ORView Profile , Zhanping Chen Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, OR Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, ORView Profile , Shekhar Borkar Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, OR Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, ORView Profile , Manoj Sachdev Department of ECE, University of Waterloo, Canada Department of ECE, University of Waterloo, CanadaView Profile , Vivek De Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, OR Microprocessor Research Labs, Intel Corporation, 5350 N.E. Elam Young Parkway, Hillsboro, ORView Profile Authors Info & Claims ISLPED '01: Proceedings of the 2001 international symposium on Low power electronics and designAugust 2001 Pages 147–152https://doi.org/10.1145/383082.383121Online:06 August 2001Publication History 39citation804DownloadsMetricsTotal Citations39Total Downloads804Last 12 Months50Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access