Memory Controller Row Hammering Mitigation via Error History
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Solution Overview
Problem
The increasing integration of memory devices leads to increased coupling effects between adjacent word lines, causing data damage due to the 'row hammering' phenomenon, where frequently enabled word lines disturb adjacent memory cells before they can be refreshed, and existing methods to address this issue result in excessive overhead.
Innovation Solution
A memory system with a memory controller and device that includes a replica table, error history storage circuit, and determination circuit to manage rows for additional refresh operations, selectively evicting rows with error histories to perform active operations and reduce data loss from row hammering without the need for excessive refresh cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the distance between adjacent word lines is reduced to increase integration, then memory integration is improved, but coupling effect between word lines increases causing row hammering
Solution Approach 1:
The patent segments the word line management by maintaining multiple tables (first table and second table) to categorize different groups of word lines. This segmentation allows selective refresh operations on specific word line groups, reducing the impact of coupling effects while maintaining high integration.
Solution Approach 2:
The patent performs preliminary classification of word lines into different tables based on their access patterns and coupling characteristics. By pre-identifying word lines that are prone to row hammering effects, the system can proactively apply refresh operations before data corruption occurs, rather than reacting after damage happens.
2Reliability
If counting method is used to identify frequently enabled rows, then row hammering detection is improved, but overhead is excessively increased
Solution Approach 1:
The patent extracts the row hammering detection function from the main memory control flow by using separate tables to track and manage word lines requiring refresh. This extraction allows the detection mechanism to operate independently without adding significant overhead to the primary memory access paths.
Solution Approach 2:
Instead of counting and refreshing all word lines equally, the patent applies partial action by selectively refreshing only those word lines identified as prone to row hammering effects. This selective approach reduces the overall refresh overhead while maintaining adequate protection against data corruption.
3Reliability
If additional refresh operations are performed on all rows, then data loss prevention is improved, but productivity is reduced
Solution Approach 1:
The patent applies local quality by differentiating refresh requirements across different word line groups. Instead of uniform refresh operations, the system applies targeted refresh operations only to word lines stored in the first table that are identified as vulnerable to row hammering, while word lines in the second table receive standard refresh treatment.
Solution Approach 2:
The patent performs partial refresh operations on only the necessary portion of word lines (those in the first table with row hammering risks) rather than refreshing all word lines. This partial action approach maintains data loss prevention for vulnerable rows while preserving overall memory productivity.
Data Source
AI summary
A memory system may include a memory system may include a memory device including a table suitable for managing rows for an additional refresh operation; and a memory controller comprising: a replica table corresponding to the table of the memory; an error history storage circuit suitable for storing an error history of the memory device; and a determination circuit suitable for determining whether to perform an active operation of a target row to be evicted from the replica table without the additional refresh operation, using the error history, when the target row is present.