SIMD Slice Enable Flags for Power and Throughput
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Solution Overview
Problem
In SIMD processing pipelines, the complexity of data dependency checking is increased due to varying latency in scalar and vector operations, leading to performance degradation and power inefficiencies, particularly when dealing with unused slices and dependencies like WAW and RAW.
Innovation Solution
Implementing enable flags to control the operation of SIMD slices, allowing for individual enabling and disabling of processing circuits, which enables flexible management of clock signals and data forwarding, thereby addressing dependency checking complexities without performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data of unused slices are pipelined without modification, then data forwarding is achieved, but power savings are difficult to achieve
Solution Approach 1:
The patent implements dynamic control of SIMD slice operation through enable flags, allowing the processor to adaptively enable or disable individual slices based on whether their results are actually needed. This dynamic switching resolves the contradiction by enabling slices only when required for data forwarding while disabling them to save power when their results are not needed, making the system both fast and energy-efficient.
Solution Approach 2:
The patent applies local quality control by allowing different slices of the SIMD processor to have different operational states (enabled or disabled) simultaneously. Each slice can be independently controlled based on its specific needs, enabling fine-grained power management while maintaining data forwarding capability where needed.
2Device complexity
If instruction issuance is delayed or stalled to allow operations to finish write-back stage, then dependency checking complexity is reduced, but significant performance degradation occurs
Solution Approach 1:
The patent implements preliminary action by performing enable flag evaluation and dependency resolution before instruction issuance. The system determines in advance which slices need to be enabled and resolves dependencies beforehand, allowing instructions to be issued without stalling while maintaining correct dependency handling.
Solution Approach 2:
The patent uses dynamic enable flags to control slice operation in real-time, allowing the processor to handle dependencies dynamically rather than through static stalling. This enables the system to maintain high throughput by keeping pipelines flowing while still correctly managing data dependencies through selective slice enabling.
3Device complexity
If additional hardware is added to read destination register and pipeline data without modification, then dependency checking complexity is addressed, but increase in stalling occurs
Solution Approach 1:
The patent performs preliminary evaluation of enable flags and dependency conditions before instructions enter the pipeline. By resolving dependencies and determining slice enablement in advance, the system avoids the need for additional stalling hardware and reduces stalling time while maintaining correct dependency handling.
Solution Approach 2:
The patent implements dynamic control mechanisms that evaluate enable flags and dependency conditions in real-time, allowing the processor to adaptively manage data flow without requiring additional static hardware for stalling. This dynamic approach reduces both hardware complexity and stalling time.
Data Source
AI summary
Methods and apparatus provide for disabling at least some data path processing circuits of a SIMD processing pipeline, in which the processing circuits are organized into a matrix of slices and stages, in response to one or more enable flags during a given cycle.