Dynamic Memory Refresh Module Optimizing Lockout Time
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Solution Overview
Problem
As memory devices increase in size, the periodic refreshing required for DRAM devices leads to a significant 'lockout time' where the memory is inaccessible, impacting system performance due to the fixed and infrequent refresh operations, which do not adapt to changing bandwidth and latency demands.
Innovation Solution
A dynamic refresh module that determines the number of memory cells to refresh and the interval based on desired bandwidth and latency characteristics, allowing for flexible refresh operations to optimize system performance by adjusting the refresh frequency and block size dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of memory cells refreshed in a single refresh operation is increased to improve coverage, then the refresh period is reduced, but the lockout time increases and memory accessibility decreases
Solution Approach 1:
The memory device is divided into multiple banks, and the refresh operation is segmented to refresh only a subset of banks (e.g., half the banks) in each refresh cycle. This segmentation allows the memory system to maintain refresh coverage while reducing the lockout time compared to refreshing all banks simultaneously.
Solution Approach 2:
The refresh operation is made dynamic by allowing the memory controller to adjust the number of banks refreshed based on system conditions. The system can dynamically switch between refreshing fewer banks (reducing lockout time) and refreshing more banks (increasing coverage) depending on performance requirements.
2Reliability
If refresh operations are performed frequently to ensure data retention, then data loss is prevented, but system performance and bandwidth are reduced
Solution Approach 1:
The system implements periodic refresh operations at optimized intervals. Instead of continuous or overly frequent refreshing, the system performs refresh operations at calculated intervals that ensure data retention while minimizing interference with normal memory operations and maintaining system performance.
Solution Approach 2:
The system performs partial refresh operations, refreshing only a portion of the memory banks at each interval rather than all banks. This partial action approach provides sufficient data retention for most applications while significantly reducing the performance impact compared to full refresh operations.
3Reliability
If the refresh interval is fixed to meet the minimum refresh period, then data retention is ensured, but adaptability to varying bandwidth and latency demands is lost
Solution Approach 1:
The refresh interval and refresh quantity are made dynamic parameters that can be adjusted based on system conditions. The memory controller can adapt the refresh strategy to varying bandwidth and latency demands while ensuring that the refresh period remains within the maximum limit required for data retention.
Solution Approach 2:
The system changes key refresh parameters (number of banks refreshed, refresh interval timing) dynamically based on operational requirements. This allows the system to optimize for either data retention or performance depending on the current workload and application needs.
Data Source
AI summary
An embodiment provided is a memory system with dynamic refreshing that includes a memory device with memory cells. The system also includes a refresh module in communication with the memory device and with a memory controller, the refresh module configured for receiving a refresh command from the memory controller and for refreshing a number of the memory cells in the memory device in response to receiving the refresh command. The number of memory cells refreshed in response to receiving the refresh command is responsive to at least one of a desired bandwidth characteristic and a desired latency characteristic.