Showing papers on "Power management published in 2000"

A survey of design techniques for system-level dynamic power management : Special section on low-power electronics and design

Abstract: Dynamic power management (DPM) is a design methodology for dynamically reconfiguring systems to provide the requested services and performance levels with a minimum number of active components or a minimum load on such components. DPM encompasses a set of techniques that achieves energy-efficient computation by selectively turning off (or reducing the performance of) system components when they are idle (or partially unexploited). In this paper, we survey several approaches to system-level dynamic power management. We first describe how systems employ power-manageable components and how the use of dynamic reconfiguration can impact the overall power consumption. We then analyze DPM implementation issues in electronic systems, and we survey recent initiatives in standardizing the hardware/software interface to enable software-controlled power management of hardware components.

A survey of design techniques for system-level dynamic power management

Abstract: Dynamic power management (DPM) is a design methodology for dynamically reconfiguring systems to provide the requested services and performance levels with a minimum number of active components or a minimum load on such components DPM encompasses a set of techniques that achieves energy-efficient computation by selectively turning off (or reducing the performance of) system components when they are idle (or partially unexploited) In this paper, we survey several approaches to system-level dynamic power management We first describe how systems employ power-manageable components and how the use of dynamic reconfiguration can impact the overall power consumption We then analyze DPM implementation issues in electronic systems, and we survey recent initiatives in standardizing the hardware/software interface to enable software-controlled power management of hardware components

Power aware page allocation

Abstract: One of the major challenges of post-PC computing is the need to reduce energy consumption, thereby extending the lifetime of the batteries that power these mobile devices. Memory is a particularly important target for efforts to improve energy efficiency. Memory technology is becoming available that offers power management features such as the ability to put individual chips in any one of several different power modes. In this paper we explore the interaction of page placement with static and dynamic hardware policies to exploit these emerging hardware features. In particular, we consider page allocation policies that can be employed by an informed operating system to complement the hardware power management strategies. We perform experiments using two complementary simulation environments: a trace-driven simulator with workload traces that are representative of mobile computing and an execution-driven simulator with a detailed processor/memory model and a more memory-intensive set of benchmarks (SPEC2000). Our results make a compelling case for a cooperative hardware/software approach for exploiting power-aware memory, with down to as little as 45% of the Energy• Delay for the best static policy and 1% to 20% of the Energy• Delay for a traditional full-power memory.

The benefits of event: driven energy accounting in power-sensitive systems

Abstract: A prerequisite of energy-aware scheduling is precise knowledge of any activity inside the computer system. Embedded hardware monitors (e.g., processor performance counters) have proved to offer valuable information in the field of performance analysis. The same approach can be applied to investigate the energy usage patterns of individual threads. We use information about active hardware units (e.g., integer/floating-point unit, cache/memory interface) gathered by event counters to establish a thread-specific energy accounting. The evaluation shows that the correlation of events and energy values provides the necessary information for energy-aware scheduling policies.Our approach to OS-directed power management adds the energy usage pattern to the runtime context of a thread. Depending on the field of application we present two scenarios that benefit from applying energy usage patterns: Workstations with passive cooling on the one hand and battery-powered mobile systems on the other hand.Energy-aware scheduling evaluates the energy usage of each thread and throttles the system activity so that the scheduling goal is achieved. In workstations we throttle the system if the average energy use exceeds a predefined power-dissipation capacity. This makes a compact, noiseless and affordable system design possible that meets sporadic yet high demands in computing power. Nowadays, more and more mobile systems offer the features of reducible clock speed and dynamic voltage scaling. Energy-aware scheduling can employ these features to yield a longer battery life by slowing down low-priority threads while preserving a certain quality of service.

Power management for throughput enhancement in wireless ad-hoc networks

Abstract: We introduce the notion of power management within the context of wireless ad-hoc networks. More specifically, we investigate the effects of using different transmit powers on the average power consumption and end-to-end network throughput in a wireless ad-hoc environment. This power management approach would help in reducing the system power consumption and hence prolonging the battery life of mobile nodes. Furthermore, it improves the end-to-end network throughput as compared to other ad-hoc networks in which all mobile nodes use the same transmit power. The improvement is due to the achievement of a tradeoff between minimizing interference ranges, reduction in the average number of hops to reach a destination, reducing the probability of having isolated clusters, and reducing the average number of transmissions (including retransmissions due to collisions). The protocols would first dynamically determine an optimal connectivity range wherein they adapt their transmit powers so as to only reach a subset of the nodes in the network. The connectivity range would then be dynamically changed in a distributed manner so as to achieve the near optimal throughput. Minimal power routing is used to further enhance performance. Simulation studies are carried out in order to investigate these design approaches. It is seen a network with such a power managed scheme would achieve a better end-to-end throughput performance (about 10% improvement with a slotted aloha MAC protocol) and lower transmit power (about an 80% Improvement) than a network without such a scheme.

Application-driven power management for mobile communication

Abstract: In mobile computing, power is a limited resource. Like other devices, communication devices need to be properly managed to conserve energy. In this paper, we present the design and implementation of an innovative transport level protocol capable of significantly reducing the power usage of the communication device. The protocol achieves power savings by selectively choosing short periods of time to suspend communications and shut down the communication device. It manages the important task of queuing data for future delivery during periods of communication suspension, and decides when to restart communication. We also address the tradeoff between reducing power consumption and reducing delay for incoming data. We present results from experiments using our implementation of the protocol. These experiments measure the energy consumption for three simulated communication patterns as well as three trace-based communication patterns and compare the effects of different suspension strategies. Our results show up to 83% savings in the energy consumed by the communication. For a high-end laptop, this can translate to 6‐9% savings in the energy consumed by the entire mobile computer. This can represent savings of up to 40% for current hand-held PCs. The resulting delay introduced is small (0.4‐3.1 s depending on the power management level).

Adaptive power management for a node of a cellular telecommunications network

Abstract: Equipment and/or functions at a node (e.g., base station) of a cellular telecommunications network are turned off or put into sleep mode during periods of low traffic in order to reduce power consumption by the node. The equipment and/or functions are then turned back on again during periods of high traffic load in order to provide the required service to users. Exemplary actions which can be taken in order to save power during the power saving mode include, for example and without limitation: 1) switching off or putting to sleep one or more MCPAs, 2) turning off one or more carriers, 3) turning off one or more sectors with regard to a frequency, 4) turning off or putting to sleep at least a portion or part of one or more circuit boards, and/or 5) reducing fan speed based upon traffic load of the node. Any one or more of these or similar actions may be taken in order to enable the node to save power when its traffic load is at a low level. Power consumption can thus be reduced.

Power-conscious joint scheduling of periodic task graphs and aperiodic tasks in distributed real-time embedded systems

Abstract: In this paper, we present a power-conscious algorithm for jointly scheduling multi-rate periodic task graphs and aperiodic tasks in distributed real-time embedded systems. While the periodic task graphs have hard deadlines, the aperiodic tasks can have either hard or soft deadlines. Periodic task graphs are first scheduled statically. Slots are created in this static schedule to accommodate hard aperiodic tasks. Soft aperiodic tasks are scheduled dynamically with an on-line scheduler. Flexibility is introduced into the static schedule and optimized to allow the on-line scheduler to make dynamic modifications to the static schedule. This helps minimize the response times of soft aperiodic tasks through both resource reclaiming and slack stealing. Of course, the validity of the static schedule is maintained. The on-line scheduler also employs dynamic voltage scaling and power management to obtain a power-efficient schedule. Experimental results show that the flexibility introduced into the static schedule helps improve the response times of soft aperiodic tasks by up to 43%. Dynamic voltage scaling and power management reduce power by up to 68%. The scheme in which the static schedule is allowed to be flexible achieves up to 3.2% more power saving compared to the scheme in which no flexibility is allowed, when both schemes are power-conscious. Our work gives an average architecture price saving of 30% over a previous approach for embedded system architectures synthesized with execution slots for hard aperiodic tasks present.

Quantitative comparison of power management algorithms

Abstract: Dynamic power management saves power by shutting down idle devices. Several management algorithms have been proposed and demonstrated to be effective in certain applications. We quantitatively compare the power saving and performance impact of these algorithms on hard disks of a desktop and notebook computers. This paper has three contributions. First, we build a framework in Windows NT to implement power managers running realistic workloads and directly interacting with users. Second, we define performance degradation that reflects user perception. Finally, we compare power saving and performance of existing algorithms and analyze the difference.

Intra-device communications architecture for managing electrical power distribution and consumption

Abstract: A power management architecture for an electrical power distribution system, or portion thereof, is disclosed. The architecture includes multiple intelligent electronic devices (“IED's”) distributed throughout the power distribution system to manage the flow and consumption of power from the system. The IED's are linked via a network to back-end servers. Power management application software and/or hardware components operate on the IED's and the back-end servers and inter-operate via the network to implement a power management application. The architecture provides a scalable and cost effective framework of hardware and software upon which such power management applications can operate to manage the distribution and consumption of electrical power by one or more utilities/suppliers and/or customers which provide and utilize the power distribution system.

System and method for power management

Abstract: A system and method for power management is described that provides for monitoring and controlling a regenerative fuel cell and at least one powered device. The power management system includes a communication interface to facilitate data transmission, a communication device for monitoring and controlling a regenerative fuel cell and at least one powered device, the communication device providing for sending data to and receiving data from at least one powered device over a communication interface, a regenerative fuel cell for providing storage and supply of electricity, and a power interface for allowing electricity generated by the regenerative fuel cell to power at least one powered device.

Power management for computer systems

Abstract: Power management approaches for computer systems having one or more processors are disclosed One power management approach provides hierarchical power management The hierarchical nature of the power management provided by the invention has various levels of power management such that power consumption of the computer system is dependent upon the amount of work placed on the processing resources of the computer system Another power management approach pertains to deterministic handshaking provided between a power manager and one or more controller units The deterministic handshaking provides for more reliable and controllable transitions between power management states which have associated power management taking place in the controller units The power management approaches are suitable for use with a single-processor computer system or a multi-processor computer system

Every joule is precious: the case for revisiting operating system design for energy efficiency

Abstract: By some estimates, there will be close to one billion wireless devices capable of Internet connectivity within five years, surpassing the installed base of traditional wired compute devices. These devices will take the form of cellular phones, personal digital assistants (PDA's), embedded processors, and "Internet appliances". This proliferation of networked computing devices will enable a number of compelling applications, centering around ubiquitous access to global information services, just in time delivery of personalized content, and tight synchronization among compute devices/appliances in our everyday environment. However, one of the principal challenges of realizing this vision in the post-PC environment is the need to reduce the energy consumed in using these next-generation mobile and wireless devices, thereby extending the lifetime of the batteries that power them. While the processing power, memory, and network bandwidth of post-PC devices are increasing exponentially, their battery capacity is improving at a more modest pace.Thus, to ensure the utility of post-PC applications, it is important to develop low-level mechanisms and higher-level policies to maximize energy efficiency. In this paper, we propose the systematic re-examination of all aspects of operating system design and implementation from the point of view of energy efficiency rather than the more traditional OS metric of maximizing performance. In [7], we made the case for energy as a first-class OS-managed resource. We emphasized the benefits of higher-level control over energy usage policy and the application/OS interactions required to achieve them. This paper explores the implications that this major shift in focus can have upon the services, policies, mechanisms, and internal structure of the OS itself based on our initial experiences with rethinking system design for energy efficiency.Our ultimate goal is to design an operating system where major components cooperate to explicitly optimize for energy efficiency. A number of research efforts have recently investigated aspects of energy-efficient operating systems (a good overview is available at [16, 20]) and we intend to leverage existing "best practice" in our own work where such results exist. However, we are not aware of any systems that systematically revisit system structure with energy in mind. Further, our examination of operating system functionality reveals a number of opportunities that have received little attention in the literature. To illustrate this point, Table 1 presents major operating system functionality, along with possible techniques for improving power consumption characteristics. Several of the techniques are well studied, such as disk spindown policies or adaptively trading content fidelity for power [8]. For example, to reduce power consumption for MPEG playback, the system could adapt to a smaller frame rate and window size, consuming less bandwidth and computation.One of the primary objectives of operating systems is allocating resources among competing tasks, typically for fairness and performance. Adding energy efficiency to the equation raises a number of interesting issues. For example, competing processes/users may be scheduled to receive a fair share of battery resources rather than CPU resources (e.g., an application that makes heavy use of DISK I/O may be given lower priority relative to a compute-bound application when energy resources are low). Similarly, for tasks such as ad hoc routing, local battery resources are often consumed on behalf of remote processes. Fair allocation dictates that one battery is not drained in preference to others. Finally, for the communication subsystem, a number of efforts already investigate adaptively setting the polling rate for wireless networks (trading latency for energy).Our efforts to date have focused on the last four areas highlighted in Table 1. For memory allocation, our work explores how to exploit the ability of memory chips to transition among multiple power states. We also investigate metrics for picking energy-efficient routes in ad hoc networks, energy-efficient placement of distributed computation, and flexible RPC/name binding that accounts for power consumption.These last two points of resource allocation and remote communication highlight an interesting property for energy-aware OS design in the post-PC environment. Many tasks are distributed across multiple machines, potentially running on machines with widely varying CPU, memory, and power source characteristics. Thus, energy-aware OS design must closely cooperate with and track the characteristics of remote computers to balance the often conflicting goals of optimizing for energy and speed.The rest of this paper illustrates our approach with selected examples extracted from our recent efforts toward building an integrated hardware/software infrastructure that incorporates cooperative power management to support mobile and wireless applications. The instances we present in subsequent sections cover the resource management policies and mechanisms necessary to exploit low power modes of various (existing or proposed) hardware components, as well as power-aware communications and the essential role of the wide-area environment. We begin our discussion with the resources of a single machine and then extend it to the distributed context.

Dynamic hardware control for energy management systems using task attributes

Abstract: A multiprocessor system (10) includes a plurality of processing modules, such as MPUs (12), DSPs (14), and coprocessors/DMA channels (16). Power management software (38) in conjunction with profiles (36) for the various processing modules and the tasks to executed are used to build scenarios which meet predetermined power objectives, such as providing maximum operation within package thermal constraints or using minimum energy. Actual activities associated with the tasks are monitored during operation to ensure compatibility with the objectives. The allocation of tasks may be changed dynamically to accommodate changes in environmental conditions and changes in the task list. As each task in a scenario is executed, a control word associated with the task can be used to enable/disable circuitry, or to set circuits to an optimum configuration.

Power management and control for a microcontroller

Abstract: A power management system for a microcontroller. The power management system includes a power management state machine for controlling a power mode of a central processing unit (CPU) and each subsystem within the microcontroller. Each microcontroller subsystem is connected to the system through a configurable peripheral interface (FPI). Each FPI includes a software configuration register (SFR) that can be configured by an operating system or application program. The SFR for the various FPIs can be preconfigured to allow the response to each of the power modes of the power management state machine to be independently controlled for each subsystem.

Digital PWM controller and current estimator for a low-power switching converter

Abstract: This paper describes design and implementation of a digital controller for an experimental low-power converter in a battery-powered system with power management. Multiple operating modes are used to maintain high efficiency over wide ranges of input voltages and loads. A current estimation technique to perform load-dependent mode switching is proposed and tested. A digital PID regulator design example is described, with emphasis on practical limitations imposed by the fixed-point arithmetic and the delay due to sampling and processing.

Power management for an implantable medical device

Abstract: A power management system and technique to manage and allocate the energy provided to various components of an implanted device during periods of low energy. The power management system includes an implantable power source delivering energy to various components within the implantable medical device, a measurement device to measure the energy of the power source, and a processor responsive to the measurement device. The processor monitors the energy level of the power source. During periods of low energy, the processor limits the energy to certain device-critical components of the implantable medical device. This minimizes the risk of damage to the power source resulting from high energy drain during periods of low energy. Further, this preserves operation of device-critical components of the implanted device during periods of low energy.

Computer screen power management through detection of user presence

Abstract: An apparatus is described for detecting presence of a user. The apparatus includes at least one thermal sensor to sense temperature around a define area of a computer system and a user presence detection subsystem coupled to the thermal sensor. The user presence detection subsystem determines presence of a user by analyzing signals output by the thermal sensor during a sampling period.

Low-power task scheduling for multiple devices

Abstract: Power management saves power by shutting down idle devices. These devices often serve requests from concurrently running tasks. Ordering task execution can adjust the lengths of idle periods and exploit better opportunities for power management. This paper presents an on-line low-power scheduling algorithm for multiple devices. Simulations show that it can save up to 33% power and reduce 40% state-transition delays. This algorithm is robust under imperfect knowledge of future requests and timing constraints; therefore, it is applicable to interactive systems.

Mechanism for providing power management through virtualization

Abstract: In one embodiment, a method for providing power management via virtualization includes monitoring the utilization of a host platform device by one or more virtual machines and managing power consumption of the host platform device based on the results of monitoring.

Dynamic power management of complex systems using generalized stochastic Petri nets

Abstract: In this paper, we introduce a new technique for modeling and solving the dynamic power management (DPM) problem for systems with complex behavioral characteristics such as concurrency, synchronization, mutual exclusion and conflict. We model a power-managed distributed computing system as a controllable Generalized Stochastic Petri Net (GSPN) with cost. The obtained GSPN model is automatically converted to an equivalent continuous-time Markov decision process. Given the delay constraints, the optimal power management policy for system components as well as the optimal dispatch policy for requests are calculated by solving a linear programming problem based on the Markov decision process. Experimental results show that the proposed technique can achieve more than 20% power saving compared to other existing DPM techniques.

Method and apparatus executing power on self test code to enable a wakeup device for a computer system responsive to detecting an AC power source

Abstract: A computer system that selectively disables power to wake on LAN (WOL) devices in the absence of AC power. In one embodiment, the computer system comprises a power supply and a power management controller. The power supply is configured to provide power to a wakeup device. The power management controller receives an AC voltage sense signal that indicates the presence or absence of an AC power source and enables the power supply to provide power to the wakeup device when the AC voltage sense signal is asserted. The power management controller preferably disables the power supply when the AC voltage sense signal is de-asserted. The computer system may operate in several states including an off state, a power on self test (POST) state, a working state, a trap state, and an armed state.

System and method for executing tasks according to a selected scenario in response to probabilistic power consumption information of each scenario

Abstract: A distributed processing system (10) includes a plurality of processing modules, such as MPUs (12), DSPs (14), and coprocessors/DMA channels (16). Power management software (38) in conjunction with profiles (36) for the various processing modules and the tasks to executed are used to build scenarios which meet predetermined power objectives, such as providing maximum operation within package thermal constraints or using minimum energy. Actual activities associated with the tasks are monitored during operation to ensure compatibility with the objectives. The allocation of tasks may be changed dynamically to accommodate changes in environmental conditions and changes in the task list.

Energy efficient design of portable wireless systems

Abstract: Portable wireless systems require long battery lifetime while still delivering high performance. The major contribution of this work is combining new it power management(PM) and it power control (PC) algorithms to trade off performance for power consumption at the system level in portable devices. First we present the formulation for the solution of the PM policy optimization based on renewaltheory. Next we present the formulation for power control (PC) of the wireless link that enables us to obtain further energy savings when thesystem is active. Finally, we discuss the measurements obtained for a set of PM and PC algorithms implemented for the WLAN card on a laptop. The PM policy we developed based on our renewal model consumes three times less power as compared to the default PM policy for the WLAN card with still high performance. Power control saves additional 53% in energy at same bit error rate. With both power control and power management algorithms in place, we observe on average a factor of six in power savings.

A distributed power management policy for wireless ad hoc networks

Abstract: This paper presents a power management scheme that maximizes energy saving in wireless ad hoc networks while still meeting the required quality of service (QoS). We assume that battery-powered devices can be remotely activated by a waking-up signal using a simple circuit based on RF tag technology. In this way, devices that are not currently active may enter a sleep state and power up only when they have pending traffic. Radio devices select different time-out values, so called sleep pattern, to enter various sleep states depending on their battery status and quality of service. The performances of the proposed policy are derived by simulation for a simple ad hoc network scenario. Results show the achieved tradeoff between power saving and traffic delay.

Intelligent switch for power management

Abstract: A method and system for managing power in a device having a power source is described. The system includes a switch and at least one controller. The switch is coupled with the power source and a portion of the device. The at least one controller is coupled with the switch and is for controlling the switch to be open or closed based on instructions provided to the controller. Thus, the switch and controller can manage the power provided to the portion of the device.

Power management fault strategy for automotive multimedia system

Abstract: A multimedia/personal computer-based system for operating information, communication, and entertainment devices in a mobile vehicle uses a power management strategy which reduces power consumption and boot-up time in a manner which facilitates use of a complex instruction set computing (CISC) processor system. A power management fault strategy detects fault conditions and restores proper operation without user intervention. A low power microprocessor off-board of the main motherboard switches a plurality of regulated voltages to the main motherboard and other devices. The main application microprocessor on the main motherboard sends periodic status messages to the low power microprocessor. Various strategies are provided for limiting attempts to correct a fault, monitor the state of the application microprocessor, and transition between states.

Spacecraft power technologies

Abstract: Environmental factors solar energy conversion chemical storage and generation systems nuclear systems static energy conversion dynamic energy conversion power management and distribution thermal management.

Computer diagnostic having an LED to provide direct visual feedback as to the status of the standby power supply when power button is actuated

Abstract: An electronic apparatus is described with a power provisioning system for powering the apparatus from an external power source, a power button connected to the power management control circuit for enabling a user to initiate transitions of the power provisioning system between at the first and second states, and an LED for providing a visual feedback to the user of the powered state of the computer; in which the LED is wired in series with a transistor to the standby supply output, the conducting state of the transistor being controlled directly by the power button so that the LED provides a direct visual feedback as to the state of the standby power supply output when the power button is actuated.

Power supply control circuit and method for cutting off unnecessary power to system memory in the power-off state

Abstract: In a computer system having a plurality of power management states, a power management control circuit includes a power management controller which manages power in accordance with the Advanced Configuration and Power Interface (ACPI) power management scheme, and includes a switching circuit that supplies a main power or a standby power to a system memory for the computer system according to a control of the power management controller. When a system state of the computer system is converted into the soft off state of the ACPI power management scheme, the power management controller cuts off power supplied to the system memory for the computer system. Therefore, it is possible to prevent unnecessary power consumption and damage to the system memory and to peripheral circuits when the system memory is removed or mounted from or upon a main board for the computer system.