DRAM Row Hammer Management via Count Data Reset
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Solution Overview
Problem
The row hammer issue in DRAM, where frequent access to one row can inadvertently alter data in adjacent rows, is not effectively managed by existing technologies, particularly due to the failure to reset count data during normal refresh operations.
Innovation Solution
A memory device with a bank of rows, each equipped with memory cells and count cells to track access frequency, and a row hammer management circuit that resets count data during normal refresh operations to mitigate the row hammer effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If count data is continuously accumulated to track row access frequency for row hammer detection, then row hammer detection capability is improved, but count data overflow and false positives occur without proper reset
Solution Approach 1:
The patent applies preliminary action by resetting count data proactively during normal refresh operations before overflow can occur. The row hammer management circuit monitors refresh operations and automatically resets count data when a row is refreshed, preventing accumulation beyond valid ranges and eliminating the need to wait for overflow conditions to trigger resets.
Solution Approach 2:
The patent implements feedback by using the refresh operation status as a trigger for count data reset. The refresh control circuit provides feedback about which rows are being refreshed, and the row hammer management circuit uses this feedback to selectively reset count data for those specific rows, ensuring accurate tracking of subsequent access patterns.
2Reliability
If count data is reset only during row hammer refresh operations, then row hammer victim rows are protected, but normal refresh operations do not contribute to preventing future row hammer attacks
Solution Approach 1:
The patent applies universality by making the normal refresh operation serve dual purposes: maintaining memory data integrity and preventing row hammer attacks. By resetting count data during every normal refresh operation, the system eliminates the need for separate row hammer prevention mechanisms, as the existing refresh infrastructure now provides both functions simultaneously.
Solution Approach 2:
The patent merges the row hammer prevention function with the normal refresh operation. Instead of treating them as separate operations, the row hammer management circuit integrates count data reset into the normal refresh flow, so that a single refresh operation accomplishes both memory maintenance and security prevention.
3Device complexity
If count data is not reset during normal refresh operations, then refresh operations remain simple, but count data continues to accumulate and causes false row hammer detections
Solution Approach 1:
The patent applies self-service by enabling the normal refresh operation to automatically reset its own count data without requiring separate intervention. The refresh control circuit's output about which rows are being refreshed is directly used by the row hammer management circuit to trigger count data reset for those same rows, making the system self-regulating and eliminating complex external control logic.
Data Source
AI summary
A memory device includes a bank that includes a plurality of rows, each row including memory cells and a set of count cells configured to store count data associated with the number of times each of the plurality of rows is accessed, and a row hammer management circuit configured to manage the count data of each row of the plurality of rows of the bank, and reset the count data corresponding to each row of the plurality of rows, in response a normal refresh operation being performed.