Asynchronous Pipeline Stage Speed Control via Completion Status
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Solution Overview
Problem
Synchronous pipelines face inefficiencies due to variable execution times across stages, leading to idle stages and wasted energy, as their performance is not optimized for diverse operations with differing latencies.
Innovation Solution
Modifying the operating speed of asynchronous pipeline stages by comparing completion statuses with adjacent stages, adjusting voltage or buffer drive strength to conserve energy or accelerate processing, based on determined completion statuses through monitoring output signals or replica critical paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous pipeline stages operate at a fixed clock rate to ensure timing synchronization, then reliability is improved, but productivity deteriorates due to idle stages waiting for slower operations
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed synchronous clock rate to variable asynchronous stage speeds. Each stage operates at its own optimal speed determined by its completion status and the status of adjacent stages, eliminating the need for all stages to wait for the slowest operation while maintaining proper data handshaking through status signals.
Solution Approach 2:
The patent changes the operating parameter from a fixed clock frequency to variable stage completion rates. By monitoring completion statuses and adjusting stage speeds dynamically, the system adapts to diverse operation latencies without requiring timing synchronization, thus improving throughput while maintaining reliability through status-based handshaking.
2Productivity
If pipeline stages operate at higher speeds to increase throughput, then productivity is improved, but use of energy deteriorates due to continuous high-speed operation of all stages
Solution Approach 1:
The patent implements dynamic speed adjustment where stages operate at high speed only when necessary (when input data is ready and downstream stages are ready to receive output). When stages are idle or waiting for data, they reduce their operating speed or enter low-power states, thereby reducing energy consumption while maintaining high throughput when actively processing.
Solution Approach 2:
The patent employs periodic action through the completion status monitoring mechanism. Stages alternately operate at high speed during active processing intervals and reduce speed during idle intervals, creating a periodic pattern of high and low energy consumption that overall reduces total energy usage while maintaining productivity.
3Productivity
If pipeline stages operate at variable speeds to match diverse operation latencies, then productivity is improved, but device complexity increases due to speed control mechanisms
Solution Approach 1:
The patent uses feedback through completion status signals that flow between adjacent stages. Each stage monitors the completion status of its input and output data, and uses this feedback to dynamically adjust its operating speed. This simple feedback mechanism enables variable speed operation without requiring complex centralized control, thus improving productivity with minimal added complexity.
Solution Approach 2:
The patent implements self-service by allowing each pipeline stage to autonomously determine its own operating speed based on local completion status information. Each stage independently adjusts its speed without requiring external control signals, simplifying the overall control architecture while enabling variable speed operation for improved throughput.
4Speed
If voltage is increased to accelerate stage operation, then speed is improved, but use of energy deteriorates due to quadratic relationship between voltage and power consumption
Solution Approach 1:
The patent applies dynamics by adjusting voltage levels in real-time based on operational needs. Instead of maintaining high voltage continuously, the system dynamically scales voltage to the minimum level required for current operations, reducing energy consumption during idle or low-demand periods while maintaining high speed when needed.
Solution Approach 2:
The patent changes the voltage parameter dynamically rather than maintaining a fixed high voltage. By monitoring completion statuses and adjusting voltage levels accordingly, the system achieves high speed operation only when necessary, thereby reducing overall energy consumption while maintaining the capability for fast operation when required.
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
Improves performance and energy efficiency by dynamically adjusting stage speeds, reducing idle time and energy consumption while maintaining optimal throughput and reducing lane divergence in SIMD pipelines.
Implementation Method 1
Modifying the operating speed of asynchronous pipeline stages by comparing completion statuses with adjacent stages, adjusting voltage or buffer drive strength to conserve energy or accelerate processing
Data Source
AI summary
An asynchronous pipeline includes a first stage and one or more second stages. A controller provides control signals to the first stage to indicate a modification to an operating speed of the first stage. The modification is determined based on a comparison of a completion status of the first stage to one or more completion statuses of the one or more second stages. In some cases, the controller provides control signals indicating modifications to an operating voltage applied to the first stage and a drive strength of a buffer in the first stage. Modules can be used to determine the completion statuses of the first stage and the one or more second stages based on the monitored output signals generated by the stages, output signals from replica critical paths associated with the stages, or a lookup table that indicates estimated completion times.