Electrical computers and digital processing systems: support – Computer power control – Power conservation
Reexamination Certificate
2000-03-31
2001-06-05
Lefkowitz, Sumati (Department: 2181)
Electrical computers and digital processing systems: support
Computer power control
Power conservation
C713S324000
Reexamination Certificate
active
06243821
ABSTRACT:
TECHNICAL FIELD
This invention relates to power management within a computer system, and is more particularly related to a system and method for using a set of data structures to obtain a desired power state in the computer system and to enable a device to wake the computer system from a low power state.
BACKGROUND OF THE INVENTION
Many of the newest and most modern computer systems are designed using a hierarchical hardware device paradigm. Under this paradigm, controllable hardware devices (devices) have physical input/output connectors that are connected to other devices in a hierarchical fashion. In other words, instead of having all devices directly connected to a processor off a single bus, the hierarchically designed computer system has a nesting of devices off of different speed busses within the computer system to optimize the performance of the overall computer system.
Power resources, such as shared power planes that energize devices within the computer system, are typically connected to the devices within the computer in a non-hierarchical fashion. For example, a single power plane may be connected to the processor while simultaneously being connected to an internal modem, a device which is nested below a bus which is ultimately connected to the same processor. The energy provided by such power resources and consumed by the devices within the computer system should be optimized to reduce the overall consumption of energy. Ideally, all devices in a computer system would have their own power resources which would be individually controlled by the operating system to turn off specific devices and minimize power consumed by the computer system as a whole. In this ideal situation, each device would be allocated a whole power resource that is individually controlled for the device.
Implementing such an ideal configuration is not practical due to the aggregate cost of controllable hardware (e.g., switches to turn on and off individual power planes, etc.) for each individual hardware device, particularly for modern portable computer systems. In other words, power resources can be shared by many devices using switching schemes. In this manner, power resources can be connected to groups of devices across the hierarchy of controllable hardware devices in modern portable computer systems. Determining which of the power resources can be turned off to minimize power consumed by the computer system can be difficult because of the relationships between devices and the power resources. Which device needs which power resources? Are any other devices affected if a particular power resource is turned off? How can the power resources be used effectively and efficiently to power only those devices that need to be energized?
One solution may be to turn off all power resources for a particular device in an effort to conserve power consumed by the computer system. However, other devices may also be connected and may need one of the power resources used by the device. Furthermore, some devices may have the capability to wake the computer system in response to a hardware event. If all power resources are removed from the device, the device may not be able to wake the computer system.
In summary, describing the relationship of the non-hierarchical power resources and the hierarchical controllable hardware devices to the operating system can be problematic when trying to manage which power resources must be on or can be turned off in a given situation. Thus, there is a need for a method for (1) identifying the power dependencies of devices within a computer system, (2) managing the power consumed within the computer system, and (3) enabling a device to wake or revive the computer system from a sleeping or low power consumption state.
SUMMARY OF THE PRESENT INVENTION
The present invention satisfies the above-described needs by providing a system and method for managing power consumption in a computer system. In one aspect of the present invention, a computer-readable medium is described on which is stored a computer program for identifying power dependencies within a computer system using a set of data structures. The computer program instructions, when executed, identify a system state data structure related to the computer system. The program instructions further determine which of the power resources must be off by reading the system state data structure. The program instructions further identify a power management data structure related to one of the devices. The program instructions further determine which power resources must be on to support the device in the selected device power state by reading the power management data structure, which preferably defines power management information related to the device.
In this manner, the power resources that must be on to support the device and the power resources that must be off in a given system power state advantageously identify the power dependencies within the computer system. These power dependencies are advantageous because they identify the non-hierarchical relationships between devices themselves and between a device and the computer system and are useful when managing power consumption within the computer system.
In another aspect of the present invention, a method is described for obtaining a desired power state of a device within a computer system. In the method, the power resources that must be on to support the device in the desired device power state are determined by reading a first data structure associated with the device. Each of these determined power resources that are not already turned on are then turned on, typically in a predetermined order. Finally, the device is placed into the desired device power state. Thus, the first data structure is used to obtain a desired power state of the device while advantageously turning on only those power resources necessary and minimizing power consumption within the computer system.
Additionally, the method includes turning off, typically in the predetermined order, each of the power resources no longer being used within the computer system. This is also advantageous because it further minimizes power consumption within the computer system.
Additionally, the method includes updating a list of the power resources in order to track changes in the status of the power resources (the number of devices using each power resource) as if the power resources that must be on have been turned on. In more detail, the step of updating the list typically involves incrementing the status of each of the power resources when that power resource must be turned on for a device and when that power resource was not previously being used by the device. The step of updating the list also typically involves decrementing the status of each of the power resources when that power resource is no longer required by the device and when the power resource was previously used by that device. The list is a useful means of managing and keeping track of multiple devices and how they are using power resources within a computer system.
In another aspect of the present invention, a computer system is provided with devices capable of waking the computer system from a system state. The system has a processor, devices that are connected to the processor, power resources that are connected to the devices, and a memory storage device connected to the processor for storing wake data structures associated with the device. In the computer system, the processor is operative to select one of the devices to wake the computer system, identify the system state which supports the selected device based upon the contents of a wake data structure associated with the selected device, and select a device power state for the selected device within the computer system (preferably based upon the contents in the corresponding wake data structure for the selected device). The processor is further operative to place the selected device within the computer system into a selected device power state and turn off all of the power re
Kilpatrick & Stockton LLP
Lefkowitz Sumati
Microsoft Corporation
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