Dual-Voltage Cache Memory Segmentation for Energy Efficiency
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Solution Overview
Problem
Current cache memory systems face challenges in reducing energy consumption while maintaining high performance and reliability, particularly in mobile devices where battery lifetime is a concern, as memory cells are not robust under supply voltage scaling and existing solutions like filter caches can increase energy consumption and degrade performance if the hit rate is low.
Innovation Solution
Implementing a cache memory system with two distinct voltage domains for memory cells, allowing for flexible operation between low-power and high-performance modes without compromising reliability, by configuring a first memory cell group to operate in a first voltage domain and a second group in a second domain, enabling dynamic switching between power-saving and standard performance modes based on processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If supply voltage is scaled down to reduce energy consumption, then energy efficiency is improved, but memory cell reliability deteriorates
Solution Approach 1:
The cache memory is divided into two distinct voltage domains: a first voltage domain with higher voltage for reliable memory cell operation, and a second voltage domain with lower voltage for energy-efficient operation. This segmentation allows different parts of the cache to operate at different voltages simultaneously, resolving the contradiction between energy efficiency and reliability.
Solution Approach 2:
Different voltage domains are assigned to different cache memory blocks based on local requirements. The first voltage domain is used for cache blocks requiring high reliability, while the second voltage domain is used for cache blocks where energy efficiency is prioritized. This local differentiation allows the system to optimize both reliability and energy consumption in appropriate regions.
2Use of energy by moving object
If filter cache is added to reduce energy consumption, then energy efficiency is improved, but system performance deteriorates due to increased access time
Solution Approach 1:
The cache system dynamically selects between different voltage domains and access paths based on runtime conditions. When energy efficiency is prioritized, the system uses the second voltage domain with lower voltage operation. When performance is critical, the system switches to the first voltage domain with higher voltage for faster access. This dynamic adaptation resolves the contradiction between energy efficiency and performance.
Solution Approach 2:
The system changes operating parameters (voltage level) based on performance requirements. By adjusting the voltage domain selection and cache access parameters dynamically, the system can optimize for either energy consumption or access speed depending on current workload characteristics, resolving the fixed trade-off in traditional filter cache designs.
3Reliability
If memory cell size is increased to improve reliability at low voltage, then reliability is improved, but cache capacity is reduced
Solution Approach 1:
The cache is segmented into different voltage domains where memory cells in the first voltage domain can use larger cell sizes for high reliability, while memory cells in the second voltage domain use smaller cell sizes for higher density. This segmentation allows the system to achieve both high reliability where needed and high capacity where energy efficiency is prioritized, resolving the contradiction between reliability and capacity.
Data Source
AI summary
A data processing apparatus is provided having a cache memory comprising a data storage array and a tag array and a cache controller coupled to the cache memory responsive to a cache access request from processing circuitry to perform cache look ups. The cache memory is arranged such that it has a first memory cell group configured to operate in a first voltage domain and a second memory cell group configured to operate in a second voltage domain that is different from the first voltage domain. A corresponding data processing method is also provided.