CPU Power State Transition Noise Reduction via Timing Randomization
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Solution Overview
Problem
Information handling systems experience annoying audible noise due to frequent CPU power state transitions, which current methods like replacing capacitors or mechanical modifications fail to adequately address, as they are costly or ineffective.
Innovation Solution
Randomizing the timing of CPU power state transitions within a predetermined time period (0.8 to 2 mS) to spread the noise across a wider frequency spectrum, using either a software module or an arbitration circuit to manage power transition commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If CPU power state transitions are performed at regular intervals to save power, then power consumption is reduced, but audible noise increases due to the peso-electric effect
Solution Approach 1:
The patent applies periodic action by implementing power state transitions at regular intervals (e.g., every 1 millisecond) to enable the CPU to enter low-power states during idle periods. This periodic throttling reduces overall power consumption while maintaining system responsiveness, directly addressing the energy efficiency aspect of the contradiction.
Solution Approach 2:
The patent changes the timing parameter of power state transitions from fixed regular intervals to randomized intervals within a specified range. This parameter modification spreads the peso-electric effects across different time points, preventing the accumulation of harmonics that cause audible noise, while still maintaining frequent transitions for power savings.
2Device complexity
If transitions between CPU power states occur at regular intervals, then power management is simplified, but harmonics from these transitions produce squealing noise
Solution Approach 1:
The system maintains periodic power state transitions but introduces randomization in the timing within each period. This approach preserves the overall periodic structure for simple power management while adding temporal variation to eliminate harmonic accumulation and associated audible noise.
Solution Approach 2:
The patent introduces dynamic timing variation to an otherwise static periodic schedule. By randomizing the exact timing of transitions within a defined window, the system maintains the dynamic adaptability needed for power management while eliminating the fixed-rhythm noise characteristic of purely periodic transitions.
3Object-generated harmful factors
If ceramic capacitors are replaced with POSCAPS to eliminate the peso-electric effect, then audible noise is reduced, but component cost increases five times
Solution Approach 1:
Instead of changing the physical capacitor type (which would increase cost), the patent changes the operational parameter of power state transition timing. By randomizing when transitions occur, the system prevents harmonic buildup from the peso-electric effect of ceramic capacitors, achieving noise reduction without modifying the capacitor technology or incurring higher component costs.
Solution Approach 2:
The patent accepts the peso-electric effect as an inherent property of ceramic capacitors but converts the potential harm into a benefit by randomizing transition timing. This approach uses the regularity of the peso-electric effect itself, distributing its effects across randomized time points rather than attempting to eliminate the effect through expensive alternative components.
4Object-generated harmful factors
If power state transitions are randomized to reduce noise, then audible noise is reduced, but power savings may be slightly impacted
Solution Approach 1:
The patent modifies the timing parameter of power state transitions from fixed to randomized values within a constrained range. This parameter change reduces audible noise by preventing harmonic accumulation while maintaining sufficiently frequent transitions to achieve meaningful power savings, balancing both objectives through optimized parameter selection.
Solution Approach 2:
The system implements partial randomization rather than complete randomness, confining transitions to a specific time window. This partial application of randomization is sufficient to eliminate audible noise harmonics while maintaining the frequency and effectiveness of power state transitions for energy savings, avoiding excessive deviation that would compromise power management efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces audible noise with minimal impact on system performance and battery life, spreading the noise frequency over a wider band while maintaining power savings.
Implementation Method 1
The peso-electric effect results when sudden changes to CPU core voltages change the linear dimensions of ceramic capacitors used to decouple power rails. Changes in the linear dimensions of capacitors translates into board vibrations which are sometimes perceived by a user as a high-pitched audible noise.
Data Source
AI summary
Audible noise related to power state transitions of an information handling system processing component, such as the central processing unit, is reduced by randomizing the time between power state transitions. Random power state transitions are managed by an operating system module that tracks the transitions and selects random times for subsequent transitions within a predetermined time range. Alternatively, an arbitrating circuit intercepts power state transition commands and arbitrates their communication at random times. Random power state transitions reduces audible noise by spreading the frequency of the noise-causing power transition events over a wider band.