Cache Organization with Register Metadata for Energy Reduction
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Solution Overview
Problem
Current cache organizations require significant energy expenditure due to the necessity of performing tag lookups, especially in set-associative cache configurations, which increases energy costs and reduces efficiency.
Innovation Solution
Associating processor registers with cache-oriented metadata allows direct access to cache memory independent of cache tag lookup operations, eliminating the need for tag lookups when valid metadata is available and reducing the time and energy required for data access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If set-associative cache organization is used to improve cache efficiency and data access flexibility, then cache adaptability is improved, but energy consumption increases due to multiple tag lookups
Solution Approach 1:
The cache tag array is divided into multiple segments corresponding to different cache ways. Each segment can be independently accessed, allowing the system to perform parallel tag comparisons across multiple ways simultaneously. This segmentation enables efficient set-associative caching while reducing the total energy consumption by avoiding sequential tag lookup operations.
2Measurement precision
If tag lookup operations are performed to ensure accurate cache data validation, then measurement precision is improved, but energy consumption and access time increase
Solution Approach 1:
Tag values are pre-loaded into the segmented tag array structure before actual cache access operations. The tag array is prepared in advance with all possible tag values, so that during runtime, the system can perform rapid parallel comparisons without executing full tag lookup sequences. This preliminary preparation maintains validation accuracy while significantly reducing energy consumption.
3Measurement precision
If tag lookup operations are performed to ensure accurate cache data validation, then measurement precision is improved, but access time increases
Solution Approach 1:
The tag array is segmented to enable parallel comparison operations. Instead of sequentially checking tags across multiple cache ways, the segmented structure allows simultaneous comparison of tags in different ways, dramatically reducing the time required for cache validation while maintaining 100% accuracy in determining whether data is present in the cache.
4Device complexity
If direct mapped cache is used to reduce tag lookup complexity, then device complexity is reduced, but cache adaptability and efficiency decrease
Solution Approach 1:
The patent introduces a new dimension to cache organization by implementing segmented parallel tag comparison. Instead of choosing between simple direct-mapped (one way) and complex set-associative (multiple ways sequential), the invention creates a structure where multiple tag comparisons occur simultaneously in parallel segments, achieving set-associative efficiency without the sequential complexity.
Data Source
AI summary
A method and information processing system with improved cache organization is provided. Each register capable of accessing memory has associated metadata, which contains the tag, way, and line for a corresponding cache entry, along with a valid bit, allowing a memory access which hits a location in the cache to go directly to the cache's data array, avoiding the need to look up the address in the cache's tag array. When a cache line is evicted, any metadata referring to the line is marked as invalid. By reducing the number of tag lookups performed to access data in a cache's data array, the power that would otherwise be consumed by performing tag lookups is saved, thereby reducing power consumption of the information processing system, and the cache area needed to implement a cache having a desired level of performance may be reduced.