Dynamic Link Width Control for Differential Serial Power Reduction

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Solution Overview

Problem

Differential serial communication links, such as those in PCI Express, consume significant power due to continuous transmission of clock information, and existing power-saving methods are limited to specific states during initialization and do not effectively reduce power consumption during active operation.

Innovation Solution

Implementing dynamic link width control logic to adjust the number of active lanes based on current communication demand, allowing for dynamic changes in link width during normal operation, bypassing certain states for reassociation without data loss, and utilizing power-saving states to reduce power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the link width is kept constant during normal operation, then system stability is maintained, but power consumption remains high

Engineering Contradiction:

Improvepower consumptionVSAvoiddynamic link width adjustment

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic link width adjustment during normal operation, allowing the communication link to transition between different widths (e.g., x16 to x8 lanes) based on current data transmission demands. This dynamic reconfiguration enables power savings by deactivating unused lanes while maintaining system stability through controlled transition protocols that ensure data integrity during width changes.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If power-saving states are entered during active operation, then power consumption is reduced, but link activation time increases

Engineering Contradiction:

Improvepower consumptionVSAvoidlink activation time

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The patent implements periodic monitoring of data transmission demands to determine when to transition between different link widths and power states. By periodically assessing actual bandwidth requirements and proactively adjusting link configuration before complete inactivity occurs, the system balances power savings with acceptable activation times, avoiding both excessive power consumption and unnecessarily long reactivation delays.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If link width is changed during normal operation, then additional power savings are achieved, but system complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidlink width control logic

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent employs feedback mechanisms where the system continuously monitors data transmission demands, bandwidth utilization, and power consumption levels. Based on this feedback, the link width control logic dynamically adjusts the active lane configuration, transitioning to narrower widths when bandwidth demands are low and expanding when higher throughput is required, thereby optimizing power efficiency while managing system complexity through intelligent control.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7480808B2Method and apparatus for managing power consumption relating to a differential serial communication link

Publication Date: 2009.01.20 ATI TECHNOLOGIES ULC

AI summary

Briefly, a method, apparatus and system for managing power corresponding to a differential serial communication link that has a link width defined for example by one or more lanes wherein the lanes are adapted to communicate clock recovery information in a data stream, determines, during normal operating conditions, such as conditions other than power on, reset or link fault conditions, a desired link width for the serial communication link and then changes the link width accordingly.