Electrical computers and digital processing systems: support – Computer power control – Power conservation
Reexamination Certificate
2001-12-03
2004-11-09
Elamin, A. (Department: 2116)
Electrical computers and digital processing systems: support
Computer power control
Power conservation
C713S300000, C713S320000, C713S321000, C713S322000, C713S324000, C713S330000
Reexamination Certificate
active
06816977
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the reduction in the power consumption of computing systems.
With the rise in prominence of mobile or portable computing devices, renewed attention has been given to the power consumption of such devices. If the power consumed by a mobile device can be reduced, the device's battery life will improve. Alternatively, more complex or faster processing can be achieved without a corresponding reduction in battery life.
While perhaps less obvious, power reduction in traditional “non-mobile” computing devices is also a desirable goal. For example, power costs and heat dissipation can be reduced in non-mobile applications by applying power reduction methods.
Most modern microprocessors provide power saving modes to reduce power consumption under low load conditions. For example, some processors have an idle state that consumes less power than the running state and in which no computation occurs. There is low latency to enter and exit the idle state, in the order of a few clock cycles. The processor changes from the idle to running state due to an interrupt, for example a built-in timer interrupt. On some processors, such as the Intel StrongArm SA-1100, the idle state is achieved by stopping the clock to the processor core.
Also provided may be a sleep state that consumes much less power than the idle state. There is usually high latency to enter or exit (or both) the sleep state, in the order of hundreds of clock cycles up to tens of milliseconds. The processor changes state from sleeping to running due to an interrupt. In processors with integrated subsystems, such as an LCD controller and communications subsystems, these subsystems are usually turned off during the sleep state. On the SA-1100, the latency to exit sleep is between 16 and 150 milliseconds, and all parts of the processor, other than the real time clock and interrupt controller are turned off. The sleep state may be used by the operating system when it the system has not been used for a while. For example, current handheld computers may power down if no user input is received for a number of minutes.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a method of reducing power consumption in a computing device including a processor, the method comprising:
determining a first duration to a next expected event in the computing device;
comparing the first duration to a minimum duration; and
if the first duration is greater than or equal to the minimum duration, then:
entering a processor sleep state for a sleep duration; and
entering a processor running state upon expiry of the sleep duration and before the next expected event.
The method may further comprise entering the processor running state before expiry of the sleep duration upon receipt of a user input. Further, at least two expected events may be synchronizing to increase a duration to the next expected event.
According to another aspect of the invention, the processor sleep state is entered only if the processor is spending more than a certain percentage of its time in a processor idle loop. Further, the sleep duration may be defined to be less than or equal to one second.
According to yet another aspect of the invention, the computing device includes a display device upon which an image is displayed during the sleep duration. The display device may be switched off if user input is not received within a predetermined shutoff time.
Still further, the computing device may include a touch input device that remains enabled during the sleep period. As for the display device, the touch input device may be disabled if user input is not received within a predetermined shutoff time.
According to another aspect of the invention, the minimum sleep duration is the duration below which it would consume more energy to enter the sleep state and subsequently enter the running state than it would be consumed to idle the processor for the same duration. If the first duration is less than the minimum duration, the processor may be idled for the first duration. Idling the processor is typically accomplished by stopping a processor clock.
According to another aspect of the invention, provided is a computing device comprising a processor, the computing device in use reducing power consumption by:
determining a first duration to a next expected event in the computing device;
comparing the first duration to a minimum duration; and
if the first duration is greater than or equal to the minimum duration, then:
entering a processor sleep state for a sleep duration; and
entering a processor running state upon expiry of the sleep duration and before the next expected event.
These and other advantages and aspects of the invention will become apparent to those skilled in the art upon a reading of the following detailed description of the invention, in conjunction with the accompanying drawings.
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Brakmo Lawrence Sivert
Wallach Deborah Anne
Elamin A.
Hewlett--Packard Development Company, L.P.
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