Retired Memory Rows for Non-Mission-Critical Data Storage
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Solution Overview
Problem
Memory devices, such as DRAM, face challenges in managing defective memory rows, where traditional error correction techniques are insufficient to handle physical defects, leading to the need for post-package repair (PPR) operations that retire entire rows despite most storage being usable.
Innovation Solution
The implementation of a memory controller that determines the suitability of retired memory rows for storing non-mission-critical data by evaluating the number of defective bits and using error masks to avoid writing data to defective locations, thereby reclaims storage capacity that would otherwise be unused.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional error correction techniques are used to handle defective memory rows, then reliability is improved, but storage capacity is lost because entire rows must be retired
Solution Approach 1:
The patent segments the memory row into usable and defective portions, allowing only the defective bits to be masked while the remaining functional bits continue to store data. This is achieved by creating a row mask that selectively disables only the defective bit locations rather than retiring the entire row, thus resolving the contradiction between reliability and storage capacity.
Solution Approach 2:
The patent applies local quality by treating different portions of the memory row differently - defective bits are masked out while functional bits remain accessible for storage. The row mask mechanism allows selective degradation of only the necessary portions (defective bits) while preserving the quality and functionality of the remaining bits, thereby maintaining both reliability and maximizing storage capacity.
2Reliability
If entire memory rows are retired due to physical defects, then reliability is improved, but storage capacity is reduced
Solution Approach 1:
The patent discards only the defective portions of memory rows by masking specific bad bits, while recovering and utilizing the remaining functional portions for data storage. This selective discarding approach recovers a significant portion of what would otherwise be lost storage capacity, resolving the contradiction between reliable defect management and usable storage space.
3Reliability
If post-package repair operations are performed to retire defective rows, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary action by identifying and masking defective bits during the manufacturing test phase before the device is shipped. The row mask information is stored in non-volatile memory and automatically applied during normal operation, eliminating the need for complex post-package repair operations and reducing device complexity while maintaining reliability.
Data Source
AI summary
Methods, apparatuses, and systems related to storing non-mission-critical data using retired memory slots are described. An apparatus includes circuitry configured to determine that a post package repair (PPR) operation, associated with a memory row of a memory device, has been requested by a host device communicably coupled to the circuitry. The memory row is associated with a physical address. The circuitry determines a location of a defective bit in the memory row. Retired row data comprising the physical address associated with the memory row and the defective bit location is maintained in non-transitory memory of the apparatus.