Fault-Tolerant Spread Spectrum Clock Signal Distribution
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Solution Overview
Problem
High performance computer systems face challenges in reliability and reduced electromagnetic emissions, particularly in incorporating clock spread spectrum with fault-tolerant global clock sources.
Innovation Solution
The system employs redundant clock sources with independently controllable spread spectrum control circuits that apply frequency dithering to clock signals, allowing for localized reduction of electromagnetic emissions and compliance with regulatory standards by spreading energy over a broader bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant clock sources are implemented for fault tolerance, then system reliability is improved, but device complexity increases
Solution Approach 1:
The system divides clock distribution into independent segments by providing separate redundant clock sources (e.g., two independent oscillators) that can operate independently. Each clock source can be selectively activated through clock selection logic, allowing the system to segment the clock distribution function and fail over between segments without affecting the entire system.
Solution Approach 2:
The patent applies spread spectrum modulation to dynamically change the frequency parameter of clock signals over time according to a pseudorandom pattern. This frequency modulation spreads the spectral content of the clock signal, reducing peak electromagnetic emissions while maintaining the clock's timing function, thereby resolving the contradiction between reliability and complexity through parameter transformation.
2Object-generated harmful factors
If spread spectrum frequency dithering is applied to clock signals, then electromagnetic emissions are reduced, but device complexity increases
Solution Approach 1:
The spread spectrum control circuit dynamically modulates the frequency parameter of the clock signal according to a pseudorandom dithering pattern. This transforms the clock signal from a pure sinusoid at a single frequency to a modulated signal with spread spectral content, reducing peak electromagnetic emissions in any single frequency band while distributing energy across a broader spectrum.
Solution Approach 2:
The spread spectrum control circuit acts as an intermediary between the clock source and the load. It receives the raw clock signal, applies frequency dithering modulation, and outputs the spread spectrum-modulated clock signal. This intermediary component handles the complexity of spread spectrum generation centrally, allowing multiple clock sources to benefit from emissions reduction without each requiring full spread spectrum capability.
3Adaptability or versatility
If independently controllable spread spectrum control circuits are provided for each clock source, then customization based on component tolerance is enabled, but device complexity increases
Solution Approach 1:
Each redundant clock source is equipped with its own independent spread spectrum control circuit that can be configured separately according to the specific requirements of the clock source and the tolerance characteristics of connected components. This allows local optimization where each clock source can use customized dithering parameters tailored to its performance characteristics and the sensitivity of its load, enabling fine-grained adaptability without requiring system-wide complexity.
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
This approach enhances system reliability through clock failover and reduces peak electromagnetic emissions, ensuring compliance with regulatory standards by randomizing instantaneous frequencies and allowing customization based on component tolerance levels.
Implementation Method 1
frequency dithering to a selected clock signal received from the redundant clock sources
Data Source
AI summary
To provide fault-tolerant, spread spectrum clock signals, a plurality of processing modules having respective spread spectrum control circuits are provided. Clock signals of redundant clock sources are provided to the plurality of processing modules. Failover control logic selects a corresponding one of the clock signals from the redundant clock sources for use in each of the processing modules. Frequency spreading is applied to the corresponding selected clock signal in each of at least some of the plurality of processing module.