US 5,954,820 A · Portable computer with adaptive demand-driven power management

Abstract

A method for managing power in a portable computer uses past access history of the various electrically-powered computer components and a prediction of future user demands to determine power-save mode entry and exit conditions. The component or the computer system keeps track of the access patterns. In the case of the display system component, such as the LCD display panel, because the access occurs when the user is watching the display panel and is thus not possible to measure directly, the accesses are measured indirectly from keyboard and/or pointing device activity. Each component access is detected and used to compute a current access frequency. The current access frequency is compared to a previously calculated and continuously updated threshold frequency. The threshold frequency is representative of the access pattern, e.g., uniform or sporadic, and is computed from equations that include adjustable gain factors. During operation of the component the appropriate power-save mode is entered when the current access frequency falls below the threshold frequency. The component can also adapt dynamically to varying workload situations, thereby saving more energy without degrading performance. This is accomplished by adjusting the gain factors parameters in response to tracking the actual performance of the system, thereby changing the threshold frequency. The component also determines when to exit a power-save mode without necessarily waiting for a user access.

Claims31

Dependent claims

A method of managing electrical power usage in a computer having a plurality of electrically powered components that are accessed for operation within the computer, the components including a central processing unit (CPU), a bus connecting the CPU to other components, memory accessible by the CPU, a keyboard and a keyboard controller that communicates keystrokes from the keyboard to the bus, at least one of the electrically powered components requiring a first level of electrical power when accessed for full operation and being capable of less than full operation in at least one reduced-power mode, and wherein an access to said at least one component when said at least one component is in said reduced-power mode requires recovery from said reduced-power mode, the method comprising:

determining the frequency of accesses to said at least one component that require full operation at said first level of electrical power;
storing a plurality of values representing a like plurality of previously determined access frequencies;
computing, from the stored values of previously determined access frequencies, an access threshold frequency;
and
reducing electrical power to said at least one component when the determined access frequency falls below the computed access threshold frequency to cause said at least one component to enter said reduced-power mode.

2 more elements

A method of managing electrical power usage in a computer having a plurality of electrically powered components that are accessed for operation within the computer, the components including a central processing unit (CPU), a bus connecting the CPU to other components, memory accessible by the CPU, a keyboard and a keyboard controller that communicates keystrokes from the keyboard to the bus, at least one of the electrically powered components requiring a first level of electrical power when accessed for full operation and being capable of entering a power-save mode of operation and exiting said power-save mode to return to full operation, and wherein an access to said at least one component when said at least one component is in said power-save mode requires recovery from said power-save mode, the method comprising the steps of:

determining the frequency of accesses to said at least one component that require full operation at said first level of electrical power;
storing a plurality of values representing a like plurality of previously determined access frequencies;
computing, from the stored values of previously determined access frequencies, a first access threshold frequency;
entering the power-save mode when the determined access frequency is less than the computed first access threshold frequency;
selecting a performance factor having a range of values, one limit of the range representing maximum power savings for said at least one component and the other limit of the range representing maximum performance for said at least one component;
and
using the selected performance factor to modify the first access threshold frequency computation, whereby the power-save mode entry behavior of said at least one component is adjusted by the selected performance factor.

4 more elements

A method of managing electrical power usage in a computer having a plurality of electrically powered components that are accessed for operation within the computer, the components including a central processing unit (CPU), a bus connecting the CPU to other components, memory accessible by the CPU, a keyboard and a keyboard controller that communicates keystrokes from the keyboard to the bus, at least one of the electrically powered components requiring a first level of electrical power when accessed for full operation and being capable of entering a power-save mode of operation and exiting said power-save mode to return to full operation, and wherein an access to said at least one component when said at least one component is in said power-save mode requires recovery from said power-save mode, the method comprising the steps of:

determining the frequency of accesses to said at least one component that require full operation at said first level of electrical power;
storing a plurality of values representing a like plurality of previously determined access frequencies;
computing, from the stored values of previously determined access frequencies, an access threshold frequency;
when the access frequency is less than the access threshold frequency, entering the power-save mode of operation;
detecting the power-save mode entrances and exits;
computing the durations of power-save modes from the detected mode entrances and exits;
computing an energy penalty if a computed power-save mode duration is less than a predetermined energy break-even time, said break-even time being the power-save mode duration required for the energy savings of said at least one component to be generally equal to the energy required for said at least one component to exit the power-save mode;
accumulating the computed energy penalties;
and
modifying the access threshold frequency when the accumulated energy penalties exceed a predetermined trip level, whereby the power-save mode entry behavior of said at least one component is dynamically adjusted from the accumulated computed energy penalties.

7 more elements

Dependencies are inferred from the claim text.

Portable computer with adaptive demand-driven power management

Life of this patent

Portable computer with adaptive demand-driven power management

Life of this patent

Abstract

Claims31