Dynamic Refresh Rate Adjustment for DRAM Row Hammer Mitigation
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Solution Overview
Problem
As memory cell feature sizes decrease, DRAM devices become more susceptible to errors due to increased activation rates causing row hammer errors, where repeated refresh intervals are insufficient to maintain stored data when activation rates exceed a certain threshold.
Innovation Solution
A memory controller is designed to detect and identify 'aggressor rows' by monitoring activation rates and adjust the refresh rate, increasing it when necessary to prevent row hammer errors, reverting back to default rates when activations subside, thus mitigating the high performance cost of unilateral increased refresh rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refresh rate is increased to prevent row hammer errors, then data integrity is improved, but performance deteriorates due to the high performance cost of unilateral increased refresh rates
Solution Approach 1:
The patent applies dynamics by making the refresh rate adjustable and adaptive rather than fixed. The memory controller dynamically changes the refresh rate based on real-time monitoring of activation rates, increasing it when row hammer risk is detected and reverting to default when the threat subsides, thus optimizing both data integrity and performance
Solution Approach 2:
The patent changes the refresh rate parameter in response to detected activation patterns. When the activation rate of a first row approaches a row hammer rate, the refresh rate is increased for affected rows to prevent errors, and later reverted to default values, allowing the system to adapt parameters based on operational conditions
2Reliability
If a unilateral increased refresh rate is applied to prevent row hammer errors, then data integrity is improved, but the performance cost increases
Solution Approach 1:
The patent applies local quality by selectively increasing the refresh rate only for specific rows that are at risk of row hammer errors, rather than uniformly increasing it for the entire memory device. This targeted approach reduces the overall performance cost while maintaining data integrity for vulnerable rows
Solution Approach 2:
The patent implements periodic action by monitoring activation rates continuously and adjusting refresh rates in periodic intervals. The refresh rate is increased only when necessary and reverted when the activation rate decreases, creating a responsive, periodic adjustment pattern that minimizes energy loss
Data Source
AI summary
A technique includes determining that a row of memory has been activated at a threshold rate. Upon reaching the threshold rate, a refresh rate for the row of memory and an adjacent row of memory may be increased. Subsequent to the increase, the refresh rate may be returned to a default rate.