Memory Device Cache to Memory Mode Switching Without Flushing
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Solution Overview
Problem
In computer systems, switching a data array from cache mode to memory mode requires flushing all dirty cache lines to main memory, increasing latency and necessitating software intervention, which is inefficient and costly in terms of performance.
Innovation Solution
A method and memory device that allow switching from cache mode to memory mode without flushing the sub-memory, using operation mode bits and line mode bits to determine access types and manage mode changes within the memory device, allowing seamless operation without data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data array is switched from cache mode to memory mode with flushing, then data coherency is maintained, but latency increases and performance degrades
Solution Approach 1:
The memory device autonomously tracks its operational mode using mode bits (cache mode bit and memory mode bit) and automatically manages data coherency through hardware-based valid bit clearing and mode switching, eliminating the need for software intervention and flushing operations
Solution Approach 2:
The patent changes the operational state parameters (mode bits) to transition between cache and memory modes. By setting the memory mode bit and clearing the cache mode bit, the system switches modes without requiring data flushing, as the parameter change itself signals the different operational requirements to the memory controller
2Adaptability or versatility
If the data array supports both cache mode and memory mode, then versatility is improved, but device complexity increases due to mode management requirements
Solution Approach 1:
The memory device is designed to perform multiple functions by supporting both cache mode and memory mode operations within the same data array structure. The same physical memory cells can be dynamically allocated to different operational modes based on system requirements, maximizing resource utilization
Solution Approach 2:
The device uses self-managed mode bits (cache mode bit and memory mode bit) that automatically indicate the operational state without requiring external software management. The memory controller independently interprets these bits to determine the appropriate access mode, reducing overall system complexity
3Reliability
If software intervention is used to maintain data coherency during mode changes, then data coherency is ensured, but overhead increases and performance decreases
Solution Approach 1:
The memory device autonomously manages data coherency through hardware-based mode bits and valid bits. When switching from cache to memory mode, the system automatically clears valid bits for cache lines that would need flushing, eliminating the need for software-driven flush operations and associated performance overhead
Solution Approach 2:
The mode bits act as intermediaries between the memory device and the controller, conveying operational mode information without requiring direct software intervention. The controller reads these bits to determine the appropriate access protocol, reducing the burden on software while maintaining data coherency
Data Source
AI summary
A method of operating a memory device that includes at least one sub-memory supporting a cache mode and a memory mode, the method including receiving a mode change signal instructing the memory device to change an operation mode of the at least one sub-memory from the cache mode to the memory mode; and changing the operation mode of the at least one sub-memory from the cache mode to the memory mode without flushing the at least one sub-memory, according to the mode change signal.