Power efficient resilient microarchitectures for PVT variability mitigation

Nowadays, the high power density and the process, voltage, and temperature variations became the most critical issues that limit the performance of the digital integrated circuits because of the continuous scaling of the fabrication technology. Dynamic voltage and frequency scaling technique is used to reduce the power consumption while different time relaxation techniques and error recovery microarchitectures are used to tolerate the process, voltage, and temperature variations. These techniques reduce the throughput by scaling down the frequency or flushing and restarting the errant pipeline. This thesis presents a novel resilient microarchitecture which is called ERSUT-based resilient microarchitecture to tolerate the induced delays generated by the voltage scaling or the process, voltage, and temperature variations. The resilient microarchitecture detects and recovers the induced errors without flushing the pipeline and without scaling down the operating frequency. An ERSUT-based resilient 16 × 16 bit MAC unit, implemented using Global Foundries 65 nm technology and ARM standard cells library, is introduced as a case study with 18.26% area overhead and up to 1.5x speedup. At the typical conditions, the maximum frequency of the conventional MAC unit is about 375 MHz while the resilient MAC unit operates correctly at a frequency up to 565 MHz. In case of variations, the resilient MAC unit tolerates induced delays up to 50% of the clock period while keeping its throughput equal to the conventional MAC unit’s maximum throughput. At 375 MHz, the resilient MAC unit is able to scale down the supply voltage from 1.2 V to 1.0 V saving about 29% of the power consumed by the conventional MAC unit. A double-edge-triggered microarchitecture is also introduced to reduce the power consumption extremely by reducing the frequency of the clock tree to the half while preserving the same maximum throughput. This microarchitecture is applied to different ISCAS’89 benchmark circuits in addition to the 16x16 bit MAC unit and the average power reduction of all these circuits is 63.58% while the average area overhead is 31.02%. All these circuits are designed using Global Foundries 65nm technology and ARM standard cells library. Towards the full automation of the ERSUT-based resilient microarchitecture, an ERSUT-based algorithm is introduced in C++ to accelerate the design process of the ERSUT-based microarchitecture. The developed algorithm reduces the design-time efforts dramatically and allows the ERSUT-based microarchitecture to be adopted by larger industrial designs. Depending on the ERSUT-based algorithm, a validation study about applying the ERSUT-based microarchitecture on the MAC unit and different ISCAS’89 benchmark circuits with different complexity weights is introduced. This study shows that 72% of these circuits tolerates more than 14% of their clock periods and 54.5% of these circuits tolerates more than 20% while 27% of these circuits tolerates more than 30%. Consequently, the validation study proves that the ERSUT-based resilient microarchitecture is a valid applicable solution for different circuits with different complexity weights

Microprocessor energy characterization and optimization through fast, accurate, and flexible simulation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 99-102).Energy dissipation is emerging as a key constraint for both high-performance and embedded microprocessor designs, requiring computer architects to consider energy in addition to performance when evaluating design decisions. A major limitation is the general difficulty in analyzing the energy impact of architectural and microarchitectural features without constructing detailed implementations and running slow simulations. This thesis first describes the design of a fast, accurate, and flexible circuit simulation tool which enables transition-sensitive studies of microprocessor energy consumption that would otherwise be impossible or impractical. With a simulation infrastructure in place, various optimizations are implemented that target the entire datapath and cache energy consumption. The individual energy optimizations are analyzed in detail, and the microprocessor design is characterized using various energy breakdowns and studies of the bit correlation between data values. This work shows that a few relatively simple energy-saving techniques can have a large impact in the implementation of an energy-efficient microprocessor. By fully characterizing the energy usage, this thesis establishes a coherent vision of microprocessor energy consumption, and serves as a basis and motivation for further energy optimizations.by Ronny Krashinsky.S.M

Implementation of verification methodologies

The increasing complexity of design elevates the importance of verification. This report explores different verification methodologies. The second chapter emphasizes the importance of testability and establishes the synthesis and DFT insertion flow using an SoC with ARM-Amber core as an example. Also, formal equivalence check is performed between the golden model, that is, RTL against its netlist. The third chapter delineates the design and formal verification of an Arbiter with APB slave configuration port. The design is extensively verified by writing SystemVerilog properties and we learn that the verification is only as good as the properties. Fourth chapter further explores formal verification with a different approach. The implemented x86 execution unit is formally verified by developing the its reference model and writing simple equality assertion checks. This approach exploits both, completeness of formal as well as includes the UVM reference model which reduces the long list of properties required for formal. The last chapter provides an approach to identify the critical registers in design. The critical flops in the design as a subset of all the registers which may have the most effect on the control flow of a module. This finds application in selecting the relevant auto-generated properties.Electrical and Computer Engineerin

Low Power Design Techniques for Digital Logic Circuits.

With the rapid increase in the density and the size of chips and systems, area and power dissipationbecome critical concern in Very Large Scale Integrated (VLSI) circuit design. Low powerdesign techniques are essential for today's VLSI industry. The history of symbolic logic and sometypical techniques for finite state machine (FSM) logic synthesis are reviewed.The state assignment is used to optimize area and power dissipation for FSMs. Two costfunctions, targeting area and power, are presented. The Genetic Algorithm (GA) is used to searchfor a good state assignment to minimize the cost functions. The algorithm has been implementedin C. The program can produce better results than NOVA, which is integrated into SIS by DCBerkeley, and other publications both in area and power tested by MCNC benchmarks.Flip-flops are the core components of FSMs. The reduction of power dissipation from flip-flopscan save power for digital systems significantly. Three new kinds of flip-flops, called differentialCMOS single edge-triggered flip-flop with clock gating, double edge-triggered and multiple valuedflip-flops employing multiple valued clocks, are proposed. All circuits are simulated using PSpice.Most researchers have focused on developing low-power techniques in AND/OR or NAND& NOR based circuits. The low power techniques for AND /XOR based circuits are still intheir early stage of development. To implement a complex function involving many inputs,a form of decomposition into smaller subfunctions is required such that the subfunctions fitinto the primitive elements to be used in the implementation. Best polarity based XOR gatedecomposition technique has been developed, which targets low power using Huffman algorithm.Compared to the published results, the proposed method shows considerable improvement inpower dissipation. Further, Boolean functions can be expressed by Fixed Polarity Reed-Muller(FPRM) forms. Based on polarity transformation, an algorithm is developed and implementedin C language which can find the best polarity for power and area optimization. Benchmarkexamples of up to 21 inputs run on a personal computer are given

Low-Power and Error-Resilient VLSI Circuits and Systems.

Efficient low-power operation is critically important for the success of the next-generation signal processing applications. Device and supply voltage have been continuously scaled to meet a more constrained power envelope, but scaling has created resiliency challenges, including increasing timing faults and soft errors. Our research aims at designing low-power and robust circuits and systems for signal processing by drawing circuit, architecture, and algorithm approaches. To gain an insight into the system faults due to supply voltage reduction, we researched the two primary effects that determine the minimum supply voltage (VMIN) in Intel’s tri-gate CMOS technology, namely process variations and gate-dielectric soft breakdown. We determined that voltage scaling increases the timing window that sequential circuits are vulnerable. Thus, we proposed a new hold-time violation metric to define hold-time VMIN, which has been adopted as a new design standard. Device scaling increases soft errors which affect circuit reliability. Through extensive soft error characterization using two 65nm CMOS test chips, we studied the soft error mechanisms and its dependence on supply voltage and clock frequency. This study laid the foundation of the first 65nm DSP chip design for a NASA spaceflight project. To mitigate such random errors, we proposed a new confidence-driven architecture that effectively enhances the error resiliency of deeply scaled CMOS and post-CMOS circuits. Designing low-power resilient systems can effectively leverage application-specific algorithmic approaches. To explore design opportunities in the algorithmic domain, we demonstrate an application-specific detection and decoding processor for multiple-input multiple-output (MIMO) wireless communication. To enhance the receive error rate for a robust wireless communication, we designed a joint detection and decoding technique by enclosing detection and decoding in an iterative loop to enhance both interference cancellation and error reduction. A proof-of-concept chip design was fabricated for the next-generation 4x4 256QAM MIMO systems. Through algorithm-architecture optimizations and low-power circuit techniques, our design achieves significant improvements in throughput, energy efficiency and error rate, paving the way for future developments in this area.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110323/1/uchchen_1.pd

Circuits and Systems Advances in Near Threshold Computing

Modern society is witnessing a sea change in ubiquitous computing, in which people have embraced computing systems as an indispensable part of day-to-day existence. Computation, storage, and communication abilities of smartphones, for example, have undergone monumental changes over the past decade. However, global emphasis on creating and sustaining green environments is leading to a rapid and ongoing proliferation of edge computing systems and applications. As a broad spectrum of healthcare, home, and transport applications shift to the edge of the network, near-threshold computing (NTC) is emerging as one of the promising low-power computing platforms. An NTC device sets its supply voltage close to its threshold voltage, dramatically reducing the energy consumption. Despite showing substantial promise in terms of energy efficiency, NTC is yet to see widescale commercial adoption. This is because circuits and systems operating with NTC suffer from several problems, including increased sensitivity to process variation, reliability problems, performance degradation, and security vulnerabilities, to name a few. To realize its potential, we need designs, techniques, and solutions to overcome these challenges associated with NTC circuits and systems. The readers of this book will be able to familiarize themselves with recent advances in electronics systems, focusing on near-threshold computing

Modeling of design-for-test infrastructure in complex systems-on-chips

Every integrated circuit contains a piece of design-for-test (DFT) infra- structure in order to guarantee the chip quality after manufacture. The DFT resources are employed only once in the fab and are usually not available during regular system operation. In order to assess the hardware integrity of a chip over its complete life- cycle, it is promising to reuse the DFT infrastructure as part of system- level test. In this thesis, the provided system, a Tricore processor from Infineon, must be partitioned and modified in order to enable the autonomous structural test of every component of the system in the field without expensive external tester