Multi-Mode Indexed Cache to Reduce Processor Conflict Misses

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Solution Overview

Problem

Existing cache systems suffer from conflict misses due to thrashing and poor capacity utilization, leading to inefficiencies in processor performance and power consumption.

Innovation Solution

Implementing a multi-mode indexed cache that dynamically adjusts indexing modes to select different cache sets for memory blocks, using disjoint subsets of memory block addresses to minimize conflict misses without requiring additional cache or circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single indexing mode is used to select cache sets, then the cache structure is simple, but conflict misses increase due to poor capacity utilization

Engineering Contradiction:
Improvecache indexing structureVSAvoidcache hit ratio
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent implements dynamic switching between multiple indexing modes (first indexing mode and second indexing mode) based on cache utilization conditions. The system transitions from a static single-mode indexing structure to a dynamic multi-mode structure that adapts to different operational states, thereby reducing conflict misses without permanently increasing structural complexity

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the indexing parameters by selecting different subsets of address bits based on the indexing mode. In the first indexing mode, a first subset of bits is used, while in the second indexing mode, a second subset of bits is used. This parameter change allows the same physical cache structure to achieve better capacity utilization under different conditions

Inventive Principle:
Principle #35Parameter changes

2Reliability

If multiple indexing modes are implemented to reduce conflict misses, then cache hit ratio improves, but device complexity increases

Engineering Contradiction:
Improvecache hit ratioVSAvoidcache indexing structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the cache indexing structure universal by enabling it to perform multiple indexing functions through mode switching. The same cache structure can operate in different indexing modes to handle different access patterns, making the system more versatile without requiring separate cache structures for each mode

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

Solution Approach 2:

The system dynamically selects between indexing modes based on real-time conditions rather than being fixed. This dynamic adaptation allows the cache to optimize its performance for different workloads while using a single unified structure, avoiding the need for multiple dedicated structures

Inventive Principle:
Principle #15Dynamics

3Reliability

If additional cache structures are added to handle conflict misses, then capacity utilization improves, but power consumption increases

Engineering Contradiction:
Improvecapacity utilizationVSAvoidpower consumption
Core Design Contradiction:
ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The patent extracts the conflict resolution function from a potential additional cache structure and implements it through software-controlled mode switching. Instead of adding physical hardware to handle conflicts, the system extracts the resolution logic and implements it through algorithmic approaches (indexing mode selection), thereby avoiding the power consumption of additional hardware

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The cache system serves itself by using existing hardware resources in different configurations rather than requiring additional dedicated structures. The same physical cache can serve different purposes through mode switching, making the system self-sufficient and avoiding the power overhead of extra components

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4400978B1Multi-mode indexed cache in a processor
Publication Date: 2025.07.16 NOKIA SOLUTIONS & NETWORKS OY
  • EP4400978B1 patent drawingFigure 1
  • EP4400978B1 patent drawingFigure 2
  • EP4400978B1 patent drawingFigure 3

AI summary

Various example embodiments for supporting processor capabilities are presented herein. Various example embodiments for supporting processor capabilities may be configured to support a multi-mode indexed cache for a processor. Various example embodiments for supporting a multi-mode indexed cache for a processor may be configured to support a multi-mode indexed cache configured as a set associative cache having a plurality of sets, where the cache is configured to support multiple indexing modes for indexing memory blocks such that, for a memory operation for a memory block, the multiple indexing modes are configured to cause selection of different ones of the plurality of sets of the cache for the memory operation for the given memory block.