Memory Row Access Tracking for Row Hammer Mitigation
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Solution Overview
Problem
Existing memory technologies face challenges in identifying and addressing 'row hammer' and 'clobber' attacks, which cause increased data degradation in nearby memory cells due to repeated access or extended activation of certain rows, leading to data loss before auto-refresh operations can occur.
Innovation Solution
Incorporating an oscillator to count the duration a row is activated, updating access counts stored in memory cells, and extending the row precharge time to ensure accurate tracking and writing of access counts, thereby accounting for both row hammer and clobber attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If repeated access to a particular memory cell or group of memory cells is performed, then data can be read and written frequently, but data degradation rate increases in nearby memory cells
Solution Approach 1:
The patent implements a feedback mechanism by tracking access patterns and degradation rates of memory cells. The system monitors which rows are accessed frequently and automatically adjusts refresh operations to target those specific rows, creating a closed-loop system that responds to actual usage patterns and prevents data degradation before it occurs.
Solution Approach 2:
The patent performs preliminary refresh operations on rows that are identified as being frequently accessed or showing signs of degradation. By proactively refreshing these rows before data degradation becomes critical, the system prevents data loss while maintaining high access rates for these frequently used memory cells.
2Reliability
If auto refresh operation is performed periodically, then data can be maintained, but memory cells affected by row hammer or clobber attacks cannot be targeted for refresh
Solution Approach 1:
The patent transforms the static auto-refresh process into a dynamic system that can adapt to different access patterns. The system continuously monitors row access patterns and degradation rates, then dynamically adjusts the refresh strategy to perform targeted refresh operations on specific rows that are showing signs of data degradation from row hammer or clobber attacks.
Solution Approach 2:
The patent applies local quality by treating different rows differently based on their access patterns and degradation characteristics. Instead of uniform refresh operations, the system identifies locally affected rows (those experiencing row hammer or clobber attacks) and applies enhanced refresh operations specifically to those rows, while maintaining standard refresh operations for other rows.
3Adaptability or versatility
If additional circuitry is added to identify memory cells affected by row hammer attack, then targeted refresh operation can be performed, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by using the existing row access tracking infrastructure for multiple purposes: tracking access patterns for performance optimization, monitoring degradation rates for reliability, and identifying rows affected by row hammer or clobber attacks for targeted refresh operations. This eliminates the need for separate dedicated circuitry for each function.
Solution Approach 2:
The patent merges the functions of access tracking, degradation monitoring, and attack detection into a unified system. By combining these functions into a single integrated approach that leverages existing hardware resources, the system achieves targeted refresh capability without proportionally increasing device complexity.
4Productivity
If extended activation of a row is performed, then more data can be accessed, but data degradation rate increases in nearby memory cells
Solution Approach 1:
The patent uses feedback from monitoring row activation duration and nearby cell degradation rates to dynamically adjust refresh operations. When extended activation is detected, the system receives feedback about the resulting degradation and automatically schedules targeted refresh operations to compensate for the additional degradation caused by extended activation.
Solution Approach 2:
The patent applies preliminary anti-action by detecting extended row activation patterns that are likely to cause clobber attacks and proactively scheduling refresh operations to counteract the harmful effects before they manifest as data loss. This preventive approach offsets the degradation caused by extended activation.
Data Source
AI summary
A value associated with a number of accesses of a word line and a length of said accesses may be stored on said word line. A timer may provide a periodic signal that increments a counter to update the value. The updated value may then be written back to the word line. In some examples, a memory device including the word lines may have a specification that prevents the word line from closing prior to writing the updated value to the word line.