A low-power reduced swing global clocking methodology

In this brief, we investigate the potential of reduced swing clock networks for low-power applications. We designed and laid out a full swing conventional and a reduced swing H-tree clock distribution network in 0.13-/spl mu/m CMOS technology operating at 500 MHz. In the reduced swing clock network, the swing was reduced in the global clock distribution network and was restored to the full swing in the local clock distribution domains. The post-layout simulation results of this research shows that a power saving of 22% under nominal operating condition is feasible.     

Variable supply-voltage scheme for low-power high-speed CMOSdigital design

This paper describes a variable supply-voltage (VS) scheme. From an external supply, the VS scheme automatically generates minimum internal supply voltages by feedback control of a buck converter, a speed detector, and a timing controller so that they meet the demand on its operation frequency. A 32-b RISC core processor is developed in a 0.4-μm CMOS technology which optimally controls the internal supple voltages with the VS scheme and the threshold voltages through substrate bias control. Performance in MIPS/W is improved by a factor of more than two compared with its conventional CMOS design     

Dual-edge triggered storage elements and clocking strategy for low-power systems

This paper describes the classification, detailed timing characterization, evaluation, and design of the dual-edge triggered storage elements (DETSE). The performance and power characterization of DETSE includes the effect of clocking at halved clock frequency and impact of load imposed by the storage element to the clock distribution network. The presented analysis estimates the timing penalty and power savings of a system based on DETSE, and gives design guidelines for high-performance and low-power application. In addition, the paper presents a class of dual-edge triggered flip-flops with clock load, delay, and internal power consumption comparable to the fastest single-edge triggered storage elements (SETSE). Our simulated results show that by halving the clock frequency, dual-edge clocking strategy can save about 50% of the power consumed by the clock distribution network, and relax the design of clock distribution system, while paying virtually no penalty in throughput.     

A multigigahertz clocking scheme for the Pentium(R) 4microprocessor

Core and I/O clock design for the Pentium(R) 4 microprocessor is described. Two phase-locked loops generate core and I/O clocks supporting concurrent multiple frequencies. A clock distribution network with skew optimization and jitter reduction is designed to achieve low clock inaccuracies for processors at frequencies ⩾2 GHz for the core and ⩾4 GHz for the rapid execution engine. A global medium clock frequency is distributed. Local clock drivers generate pulsed or regular (nonpulsed) clocks at fast, medium, and slow frequencies. A 3.2-GB/s system bus is achieved using a dedicated I/O phase-locked loop with glitch protection and detection. Silicon speed path tools and clock debug features are designed to enable a short debug cycle     

Half-swing clocking scheme for 75% power saving in clockingcircuitry

We propose a half-swing clocking scheme that allows us to reduce power consumption of clocking circuitry by as much as 75%, because all the clock signal swings are reduced to half of the LSI supply voltage. The new clocking scheme causes quite small speed degradation, because the random logic circuits in the critical path are still supplied by the full supply voltage. We also propose a clock driver which supplies half-swing clock and generates half V_DD by itself. We confirmed that the half-swing clocking scheme provided 67% power saving in a test chip fabricated with 0.5 μm CMOS technology, ideally 75%, in the clocking circuitry, and that the degradation in speed was only 0.5 ns by circuit simulation. The key to the proposed clocking scheme is the concept that the voltage swing is reduced only for clocking circuitry, but is retained for all other circuits in the chip. This results in significant power reduction with minimal speed degradation     

多移动终端笔记数据的同步方案设计

本文主要针对安卓个人云笔记应用的笔记数据的同步问题,包括多个移动终端的笔记数据的同步,同步冲突等,采用乐观复制,矢量时钟等技术,根据笔记是包含文本和若干附件的富媒体笔记的特点,提出了合适的数据模型,采用差量传输方式,设计了一套可行的同步方案.     

A dictionary-based en/decoding scheme for low-power data buses

As bus lengths on multihundred-million transistor systems-on-a-chip (SoC) grow, and as interwire capacitances of sub-0.10 /spl mu/m technologies advance, the resulting high-switching capacitances of buses (and interconnects in general) have a nonnegligible impact on the power consumption of a whole SoC. This trend has been recognized and recently addressed by various research groups. We address this problem by introducing our bus encoding technique, adaptive dictionary-encoding scheme "ADES" that minimizes the power consumption of data buses through a dictionary-based encoding technique. Based on exploration of data properties on buses, our technique saves on average more than 25% of bus energy compared to the nonencoded cases using a large set of real-world applications for both address and data buses. Furthermore, we compare our technique to the best-known data bus encoding techniques to date and we find that it exceeds all of them in terms of energy savings for the same set of applications.     

Novel scheme for low-power classified vector quantisation imagecoding

A novel scheme for low-power image coding and decoding based on classified vector quantisation is presented. The main idea is the replacement of the memory accesses to large background memories (most power-consuming operations), by arithmetic and/or application-specific computations. Specifically, the proposed image coding scheme uses small sub-codebooks to reduce the memory requirements and memory-related power consumption in comparison with classical vector quantisation schemes. By applying simple transformations on the codewords during coding, the proposed scheme extends the small sub-codebooks, compensating for the quality degradation introduced by their small size. Thus, the main coding task becomes computation-based rather than memory-based, leading to a significant reduction in power consumption. The proposed scheme achieves image qualities comparable with, or better than, those of traditional vector quantisation schemes, as the parameters of the transformations depend on the image block under coding, and the small sub-codebooks are dynamically adapted each time to this specific image block. The main disadvantage of the proposed scheme is the decrease in the compression ratio in comparison with classical vector quantisation. A joint (quality-compression ratio) optimisation procedure is used to keep this side-effect as small as possible     

A synchronous approach for clocking VLSI systems

Presents a synchronous solution for clocking VLSI systems organized as distributed systems. This solution avoids the drawbacks of the self-timed approach. These VLSI systems are constituted of modules which represent synchronous areas driven by their own fast clock, interconnected by a synchronous communication mechanism driven by a slow clock. In order to avoid the risk of metastability in flip-flop between the modules and the communication mechanism, the author suggests to resynchronize the phase of each module clock on the transitions of the communication clock by a phase locked loop circuitry added to each module.     

Segmented bus design for low-power systems

This paper proposes a bus-segmentation method that efficiently reduces the switched capacitance on the bus. The power consumed by the bus can, therefore, be substantially reduced. The basic idea of bus segmentation is to partition the bus into several bus segments separated by pass transistors. Highly communicating devices are located to adjacent bus segments, thus, most data communication can be achieved by switching a small portion of the bus segments. As a result, power consumption and critical path delay are both reduced. Experimental results obtained by simulating a delay model and a power model demonstrate that the proposed segmented bus system reduces bus power by about 60%-70% and improves critical bus delay by about 10%-30%     

A design for high-speed low-power CMOS fully parallelcontent-addressable memory macros

Described is a design for high-speed low-power-consumption fully parallel content-addressable memory (CAM) macros for CMOS ASIC applications. The design supports configurations ranging from 64 words by 8 bits to 2048 words by 64 bits and achieves around 7.5-ns search access times in CAM macros on a 0.35-μm 3.3-V standard CMOS ASIC technology. A new CAM cell with a pMOS match-line driver reduces search rush current and power consumption, allowing a NOR-type match-line structure suitable for high-speed search operations. It is also shown that the CAM cell has other advantages that lead to a simple high-speed current-saving architecture. A small signal on the match line is detected by a single-ended sense amplifier which has both high-speed and low-power characteristics and a latch function. The same type of sense amplifier is used for a fast read operation, realizing 5-ns access time under typical conditions. For further current savings in search operations, the precharging of the match line is controlled based on the valid bit status. Also, a dual bit switch with optimized size and control reduces the current. CAM macros of 256×54 configuration on test chips showed 7.3-ns search access time with a power-performance metric of 131 fJ/bit/search under typical conditions     

A new systematic design approach for low-power analog integrated circuits

In this paper, a new design approach for systematic design and optimization of low-power analog integrated circuits is presented based on the proper combination of a simulation-equation based optimization algorithm using geometric programming as an optimization approach and HSPICE as a simulation and verification tool by a knowledge-based transistor sizing tool which uses physical-based gm/I_D characteristic in all regions of transistor operation to increase the accuracy in a reasonable simulation time. The proposed design methodology is successfully used for automated design and optimization of an operational amplifier with hybrid-cascode compensation using 0.18 μm CMOS technology parameters with the main purpose of minimizing the power consumption of the circuit.     

Issues for low-power CAD tools: A system-level design study

A case study in low-power system-level design is presented. We detail the design of a low-power embedded system, a touchscreen interface device for a personal computer. This device is designed to operate on excess power provided by unused RS232 communication lines. We focus on the design and measurement procedures used to reduce the power requirements of this system to less than 50 mW. Additionally, we highlight opportunities to use system-level design and analysis tools for low-power design and the obstacles that prevented using such tools in this design.     

A weakness in the Bresson-Chevassut-Essiari-Pointcheval's Group Key Agreement scheme for low-power mobile devices

In this letter, we show that Bresson-Chevassut-Essiari-Pointcheval's Group Key Agreement scheme does not meet the main security properties: implicit key authentication, forward secrecy and known key security. Also, we propose an improved version, which fixes the security flaws, found in the scheme.     

Dynamic biasing scheme for high-speed= low-power switched-capacitor stages

A scheme is proposed for adjusting the bias current of the op-amp in a switched-capacitor stage so that it follows the swing of the input signal, minimising the power consumption of the stage. Simulations indicate that a 60% power saving is possible using the method     

Technology for the design of low-power circuits

Operation of integrated circuits at micropower levels requires transistors with adequate current gain at collector currents of 1 /spl mu/A and less and resistors of the order of 1 M/spl Omega/ within reasonable areas. Factors affecting current gain at low currents are discussed and design criteria presented that optimize gain at low collector current. A benefit of micropower operation is low-current noise. Factors tending to optimize noise performance are discussed. In order to obtain voltage gain at low collector current, high values of load resistance are required. Both passive and active loads suitable for incorporation in micropower integrated circuits are discussed.     

An MTCMOS technology for low-power physical design

Multi-threshold CMOS (MTCMOS) technology is an effective sub-threshold leakage power reduction method in CMOS circuits, which satisfies high-performance and low-power design requirements. The optimization of virtual supply network plays an important role in MTCMOS low-power design. Existing low-power works are mainly on gate level, without any optimization on physical design level, which can lead to a large amount of virtual supply networks. Merging the objective of virtual networks minimization into physical design, this paper presents (1) a low-power-driven physical design flow; (2) a novel low-power placement to simultaneously place standard cells and sleep transistors; and (3) the sleep transistor relocation technique to further reduce the virtual supply networks. Experimental results are promising for both achieving up to 28.15% savings for virtual supply networks and well controlling the increase of signal nets.     

Discrete-time battery models for system-level low-power design

For portable applications, long battery lifetime is the ultimate design goal. Therefore, the availability of battery and voltage converter models providing accurate estimates of battery lifetime is key for system-level low-power design frameworks. In this paper, we introduce a discrete-time model for the complete power supply subsystem that closely approximates the behavior of its circuit-level continuous-time counterpart. The model is abstract and efficient enough to enable event-driven simulation of digital systems described at a very high level of abstraction and that includes, among their components, also the power supply. The model gives the designer the possibility of estimating battery lifetime during system-level design exploration, as shown by the results we have collected on meaningful case studies. In addition, it is flexible and it can thus be employed for different battery chemistries