Reconfigurable Fetch Pipeline Cache Access Mode Selection

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Solution Overview

Problem

Current computing devices face challenges in optimizing power consumption and performance due to the inefficiencies in cache access modes, particularly in switching between parallel and serial load operations, which affect data access speed and power usage based on the number of instructions and active threads.

Innovation Solution

A reconfigurable fetch pipeline that dynamically switches between parallel and serial load operations based on the number of instructions in the issue queue, active threads, power saving modes, and user inputs, allowing for adaptive cache access modes to optimize power usage and data access speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If parallel cache access mode is used to access tag array and data array simultaneously, then data access speed is improved, but power consumption increases

Engineering Contradiction:
Improvedata access speedVSAvoidpower consumption
Core Design Contradiction:
SpeedVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic switching between parallel and serial cache access modes based on real-time system conditions. The mode selection circuit determines whether to operate in parallel mode (higher speed, higher power) or serial mode (lower speed, lower power) by evaluating metrics such as cache hit rates, power consumption thresholds, and system workload, allowing the system to adaptively optimize the trade-off between speed and power consumption.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of the cache system by switching between different access modes. When the system determines that power savings are prioritized, it transitions from parallel access (both tag and data arrays accessed simultaneously) to serial access (tag array accessed first, then data array), thereby reducing power consumption while maintaining acceptable performance through parameter adaptation.

Inventive Principle:
Principle #35Parameter changes

2Use of energy by moving object

If serial cache access mode is used to access tag array then data array sequentially, then power consumption is reduced, but data access speed decreases

Engineering Contradiction:
Improvepower consumptionVSAvoiddata access speed
Core Design Contradiction:
Use of energy by moving objectVSSpeed

Solution Approach 1:

The system dynamically adjusts the cache access mode based on real-time conditions. When power consumption needs to be reduced and system metrics indicate that serial access is acceptable (e.g., lower workload, acceptable latency thresholds), the system switches to serial mode where the tag array is accessed first followed by the data array, thereby reducing power consumption while maintaining adequate performance.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent modifies the access pattern parameters by transitioning from simultaneous access to sequential access. This parameter change allows the system to operate in a lower-power state by accessing the tag array first and then the data array in sequence, accepting a trade-off in access speed in exchange for reduced power consumption when system conditions permit.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If cache access mode is fixed, then device complexity is reduced, but adaptability to different workloads decreases

Engineering Contradiction:
Improvecontrol logic complexityVSAvoidworkload adaptability
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamic adaptability to fixed cache structures by implementing a mode selection mechanism that adjusts access patterns based on workload characteristics. The system monitors performance metrics and power consumption levels, then dynamically selects between parallel and serial access modes, enabling the fixed cache hardware to adapt to varying workload demands without requiring complex reconfiguration of the underlying cache architecture.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The cache system achieves multi-functionality by incorporating a mode selection circuit that enables the same cache hardware to operate in multiple access modes (parallel and serial). This universal design allows the fixed cache structure to serve different workload requirements efficiently, providing both high-performance parallel access when needed and power-efficient serial access when appropriate, without requiring separate dedicated cache structures for each mode.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP3149594B1Method and apparatus for cache access mode selection
Publication Date: 2019.11.27 QUALCOMM INC
  • EP3149594B1 patent drawingFigure 1
  • EP3149594B1 patent drawingFigure 2
  • EP3149594B1 patent drawingFigure 3

AI summary

A particular method includes selecting between a first cache access mode and a second cache access mode based on a number of instructions stored at an issue queue, a number of active threads of an execution unit, or both. The method further includes performing a first cache access. When the first cache access mode is selected, performing the first cache access includes performing a tag access and performing a data array access after performing the tag access. When the second cache access mode is selected, performing the first cache access includes performing the tag access in parallel with the data array access.