Word Line Access Counters for Row Hammer Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing memory technologies face challenges in identifying and refreshing memory cells affected by 'row hammer' and 'clobber' attacks, which lead to increased data degradation in nearby memory cells.
Innovation Solution
The implementation of count value memory cells and a count control circuit that track access counts and activation times of word lines, allowing for the identification of aggressor rows and targeted refresh operations to mitigate data degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional circuitry is added to identify memory cells affected by row hammer attacks, then the ability to detect and refresh affected cells is improved, but the device complexity increases
Solution Approach 1:
The patent embeds count value memory cells within the existing memory array structure, nesting the tracking functionality inside the memory cells themselves rather than adding separate external tracking circuits. This allows the system to monitor word line access patterns while minimizing additional circuitry overhead.
Solution Approach 2:
The count value memory cells serve multiple functions: they store data like regular memory cells and simultaneously track the number of times their associated word lines have been accessed. This multi-functionality eliminates the need for separate dedicated tracking circuits for each word line.
2Measurement precision
If tracking mechanisms are implemented to monitor word line accesses, then the precision of identifying aggressor rows is improved, but the device complexity increases
Solution Approach 1:
The counting mechanism is nested within the memory cell structure itself, using the same physical infrastructure (transistors, capacitors) to perform both data storage and access counting functions, thereby achieving precise tracking without proportionally increasing device complexity.
Solution Approach 2:
The memory cells automatically update their own count values whenever their associated word lines are accessed, eliminating the need for external controllers or separate tracking circuits to monitor each word line individually.
3Reliability
If targeted refresh operations are performed on affected memory cells, then data degradation is reduced, but the loss of time for refresh operations increases
Solution Approach 1:
The system proactively identifies word lines that have been accessed frequently (aggressor rows) and pre-refreshes their neighboring memory cells before data degradation occurs, rather than waiting for errors to manifest. This prevents rather than repairs damage.
Solution Approach 2:
Instead of performing blanket refresh operations across the entire memory array, the system applies refresh operations locally only to memory cells adjacent to identified aggressor word lines, minimizing the time and resources required for refreshing while protecting only the vulnerable cells.
4Measurement precision
If count value memory cells are used to track activations, then the measurement precision of activation tracking is improved, but the quantity of substance (memory resources) increases
Solution Approach 1:
Each count value memory cell serves dual purposes: storing user data and tracking the activation count of its associated word line. This eliminates the need for separate tracking memory structures and achieves precise monitoring without increasing the total number of memory cells required.
Data Source
AI summary
Counters may be provided for individual word lines of a memory for tracking word line accesses. In some examples, multiple counters may be provided for individual word lines. In some examples, the counters may be included on the word lines. The counters may be incremented responsive to word line accesses in some examples. In some examples, the counters may be incremented responsive for a time period for which a word line is held open. In some examples, the counters may be incremented responsive to both word line accesses and time periods for which the word line is held open. In some examples, count values for the counters may be written back to the counters after incrementing. In some examples, the count values may be written back prior to receiving a precharge command.