DRAM Victim Point Table Targeted Refresh Mitigates Row Hammer
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Solution Overview
Problem
As integration density increases in dynamic random access memory (DRAM), the gap between cells decreases, leading to interference from adjacent cells or wordlines, which affects data reliability and makes it difficult to restrict access to specific addresses, resulting in row hammer disturbance and refresh property issues.
Innovation Solution
A memory device and system that utilize a victim point table to calculate and accumulate victim points for target row addresses, allowing for a targeted refresh operation to mitigate row hammer disturbance and prevent double-sided row hammer attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If integration density is increased, then storage capacity is improved, but interference from adjacent cells increases
Solution Approach 1:
The patent applies preliminary action by performing refresh operations on victim rows before interference from adjacent rows can cause data corruption. The system monitors access patterns and proactively identifies rows that are likely to be affected by row hammer attacks, scheduling refresh operations in advance to prevent data loss rather than reacting after damage occurs.
Solution Approach 2:
The patent implements feedback mechanisms by monitoring access patterns and using this information to dynamically adjust refresh strategies. The system tracks which rows are accessed frequently and uses this feedback to identify potential victim rows that need prioritized refresh operations, creating a closed-loop system that adapts to changing access patterns.
2Reliability
If refresh operations are performed frequently, then data reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies local quality by performing refresh operations selectively on specific victim rows rather than uniformly refreshing all rows. The system identifies and targets only the rows that are most likely to be affected by interference based on access patterns, concentrating refresh resources on high-risk areas while leaving low-risk rows alone, thus reducing overall energy consumption.
Solution Approach 2:
The patent uses partial action by performing refresh operations on only the necessary portion of the memory array - specifically the victim rows that have been identified as at risk. Rather than refreshing the entire memory array periodically, the system performs targeted partial refreshes only on rows that show signs of being affected by row hammer attacks.
3Object-affected harmful factors
If access to specific addresses is restricted, then row hammer disturbance is reduced, but access flexibility is worsened
Solution Approach 1:
The patent introduces an intermediary mechanism - the refresh controller - that mediates between normal access operations and row hammer protection. The controller monitors access patterns, identifies when row hammer attacks are occurring, and automatically schedules refresh operations on victim rows without interfering with normal read/write operations. This intermediary layer enables protection while maintaining full access flexibility.
Data Source
AI summary
A memory device includes a memory cell array including a plurality of memory cells connected to a plurality of wordlines and a plurality of bitlines, a target row refresh logic circuit configured to select a target row address from among a plurality of target row addresses as a refresh row address based on victim point values, and perform a refresh operation on first memory cells of the plurality of memory cells connected to a wordline of the plurality of wordlines indicated by the refresh row address, a victim point table configured to store the victim point values for the target row addresses, and a victim point accumulator configured to receive a first row address from an external device, and accumulate a first victim point value for at least one target row address corresponding to the first row address during a unit time period.