Cache Sequential Access Detector Power Reduction
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Solution Overview
Problem
Power management in integrated circuits, particularly in cache arrays, faces challenges in reducing power consumption while maintaining high processor performance, as sequential cache accesses lead to redundant operations that consume unnecessary power.
Innovation Solution
Implementing a cache system with a sequential access detector that inhibits access to the tag array and data array during sequential operations, allowing previously retrieved data to be used instead of performing redundant tag comparisons and data retrievals, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the processor implements caches to improve performance, then access speed is improved, but power consumption increases due to multiple tag value comparisons, word-line discharges, and circuit operations
Solution Approach 1:
The patent applies dynamics by making the cache system adaptive to access patterns. The sequential access detector dynamically identifies sequential access patterns, and the system dynamically adjusts its behavior by inhibiting redundant tag array accesses and data array reads when sequential patterns are detected. This dynamic adaptation allows the cache to maintain high access speed for sequential operations while reducing power consumption by avoiding unnecessary circuit operations.
2Reliability
If redundant tag comparisons and data retrievals are performed during sequential accesses, then cache functionality is maintained, but power consumption increases unnecessarily
Solution Approach 1:
The patent extracts and eliminates redundant operations from the cache access process. When sequential access patterns are detected, the system extracts only the necessary tag comparison (using stored tag values) and eliminates redundant data array reads and tag array accesses. This selective removal of unnecessary operations maintains cache functionality while significantly reducing power consumption by avoiding redundant word-line discharges and circuit operations.
Solution Approach 2:
The patent applies partial action by performing only the necessary subset of cache operations. Instead of fully accessing both tag and data arrays for every sequential access, the system performs partial operations - using stored tag values for comparison and inhibiting data array reads when the data is already available. This partial action approach maintains reliability while reducing energy loss from excessive operations.
3Reliability
If the tag array and data array are accessed for every cache operation, then complete cache functionality is ensured, but power consumption increases due to redundant operations
Solution Approach 1:
The patent segments the cache access operations into distinct functional parts: tag comparison, data retrieval, and sequential access detection. By segmenting these operations, the system can selectively enable or inhibit specific segments based on access patterns. During sequential accesses, the system segments out the redundant data array read and tag array access operations, maintaining only the essential tag comparison functionality. This segmentation allows the cache to ensure operational completeness while reducing power consumption by disabling unnecessary segments.
Data Source
AI summary
In some embodiments, a cache may include a tag array and a data array, as well as circuitry that detects whether accesses to the cache are sequential (e.g., occupying the same cache line). For example, a cache may include a tag array and a data array that stores data, such as multiple bundles of instructions per cache line. During operation, it may be determined that successive cache requests are sequential and do not cross a cache line boundary. Responsively, various cache operations may be inhibited to conserve power. For example, access to the tag array and/or data array, or portions thereof, may be inhibited.