Memory Controller Row-Hammer Defense via Distance-Based Refresh
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Solution Overview
Problem
Existing memory systems face inefficiencies in preventing the row-hammer phenomenon, where data loss occurs due to high activation frequencies of specific word lines, as they apply uniform refresh rates to all adjacent word lines without considering physical distance, leading to reduced refresh efficiency and accuracy.
Innovation Solution
A memory system that adjusts refresh rates for adjacent word lines based on their physical distance from a target word line, using a memory controller to generate sampling addresses, calculate adjacent addresses, and perform targeted refresh operations according to row-hammer data, optimizing refresh operations and minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uniform refresh rates are applied to all adjacent word lines, then row-hammer phenomenon prevention is simplified, but refresh efficiency and accuracy deteriorate due to unnecessary refresh operations on distant word lines
Solution Approach 1:
The patent applies local quality by setting different refresh rates for adjacent word lines based on their physical distance from the target word line. Word lines closer to the target receive higher refresh rates, while those farther away receive lower rates. This is implemented through a refresh rate setting unit that configures distinct refresh intervals for different spatial regions, optimizing refresh efficiency by focusing resources where the row-hammer effect is most severe.
Solution Approach 2:
The patent segments the adjacent word lines into multiple groups based on their distance from the target word line. Each group is assigned a different refresh rate, creating a segmented refresh strategy. This segmentation allows the system to apply differentiated refresh policies to different spatial zones, improving overall refresh efficiency while maintaining protection against row-hammer attacks.
2Reliability
If refresh operations are performed on all adjacent word lines, then row-hammer defense coverage is maximized, but power consumption increases due to unnecessary refresh operations
Solution Approach 1:
The patent reduces power consumption by applying local quality principles to the refresh operation. Instead of uniformly refreshing all adjacent word lines, the system applies refresh operations selectively based on distance from the target word line. Word lines within a first distance threshold receive refresh operations, while those beyond this threshold do not, thereby reducing unnecessary power consumption while maintaining adequate defense capability.
Solution Approach 2:
The patent implements partial action by performing refresh operations only on a subset of adjacent word lines that fall within the first distance threshold from the target word line. This partial refresh strategy is sufficient to prevent row-hammer effects in the most vulnerable regions while avoiding the excessive power consumption that would result from refreshing all adjacent word lines uniformly.
3Measurement precision
If distance-based refresh rate variation is implemented, then refresh accuracy is improved, but control circuit complexity increases
Solution Approach 1:
The patent achieves high refresh rate precision through local quality by configuring distinct refresh rates for different distance zones. The refresh rate setting unit precisely controls the refresh intervals for word lines at different distances from the target, ensuring that each region receives the appropriate refresh frequency. This precise local control improves refresh accuracy without requiring overly complex global control mechanisms.
Data Source
AI summary
A memory system includes: a memory device suitable for providing row-hammer data to set refresh rates for adjacent word lines of a target word line, and performing a target refresh operation on one or more word lines corresponding to a first row-hammer address according to a first target refresh command; and a memory controller suitable for generating a plurality of sampling addresses by sampling an active address, generating a plurality of counting values by comparing the sampling addresses with the active address, calculating a plurality of adjacent addresses corresponding to the sampling addresses based on the counting values and the row-hammer data, and providing the adjacent addresses as the first row-hammer address with the first target refresh command.