Hardware Power Management for CPU Interrupts in Reduced Power States
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Solution Overview
Problem
Limited-powered devices, such as laptops and smartphones, face challenges in managing power consumption due to computationally intensive applications, leading to short battery life, as existing methods for reducing power consumption are inefficient and can result in unpredictable CPU behavior during power-down processes.
Innovation Solution
The CPU can be placed into a reduced power state independently of other components, with designated events triggering a hardware-based power management system to restore full power, allowing it to respond to interrupt events without software delays, thus conserving power and ensuring orderly power-down transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the CPU is placed into a reduced power state to conserve power, then power consumption is reduced and battery life is extended, but the CPU cannot respond to interrupt events that may occur while it is powered down
Solution Approach 1:
A hardware-based power management system acts as an intermediary between the CPU and interrupt events. When the CPU is in reduced power state, the power management system monitors for interrupt events and automatically restores full power to the CPU when an interrupt occurs, ensuring the CPU can respond to events even while primarily powered down
Solution Approach 2:
The system pre-configures the power management hardware to automatically restore power to the CPU when specific interrupt events occur. This preliminary setup allows the CPU to remain powered down until absolutely necessary, maximizing power savings while ensuring immediate responsiveness when events require attention
2Use of energy by moving object
If the CPU is placed into a reduced power state using software control, then power consumption is reduced, but the transition process may cause unpredictable CPU behavior
Solution Approach 1:
The patent replaces software-based power management control with a hardware-based power management system. This hardware system autonomously handles the power state transitions and interrupt monitoring, eliminating the unpredictable behavior associated with software control while maintaining power savings benefits
Solution Approach 2:
The power management hardware operates autonomously to monitor interrupt events and control CPU power states without requiring software intervention. The system serves itself by automatically restoring power when interrupts occur and maintaining power savings when no events are pending, ensuring predictable and reliable operation
3Reliability
If the CPU remains at full power to handle interrupt events, then responsiveness to events is maintained, but power consumption increases and battery life decreases
Solution Approach 1:
The system dynamically adjusts the CPU power state based on the presence or absence of interrupt events. The CPU transitions between reduced power state (when no events are pending) and full power state (when events occur), optimizing the balance between power consumption and event responsiveness in real-time
Data Source
AI summary
To reduce power consumption, a processor can be placed into a reduced power state. Before doing so, interrupt events can be designated as wakeup events. While the processor is in the reduced power state, if an event designated as a wakeup event occurs, then a signal is directed to a wakeup event handler instead of to an interrupt handler. In response to the signal, the wakeup event handler causes power to be restored to the processor, so that the event can be subsequently serviced.