Memory Defect Tables for Selective Location Remapping
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Solution Overview
Problem
Conventional memory systems with modular memory modules face inefficiencies in maintaining reliability due to memory failures, as entire modules are often replaced upon detection of defects, leading to high costs and performance impact, especially in large-scale systems.
Innovation Solution
The implementation of memory defect tables that store and map defective memory locations to non-defective ones, allowing for selective replacement and allocation of memory resources, thereby increasing fault-tolerance and reducing service requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zero defect tolerance is employed and entire memory modules are replaced upon defect detection, then system reliability is maintained, but cost and performance are significantly impacted
Solution Approach 1:
The patent segments the memory module into individually addressable memory locations and creates a defect table that tracks defects at the location level rather than module level. This allows the system to identify and isolate only the specific defective locations while keeping the rest of the memory module operational, thus maintaining productivity while ensuring reliability.
Solution Approach 2:
The patent applies local quality by treating each memory location independently with its own defect status tracking. The defect table stores location-specific defect information, enabling the system to apply different quality treatments (defective vs. non-defective) to different parts of the same memory module, allowing continued use of healthy memory locations.
2Reliability
If entire memory modules are replaced upon defect detection, then reliability is ensured, but resource utilization deteriorates
Solution Approach 1:
The patent divides the memory module into addressable locations and tracks defects at this granular level. The defect table enables the system to segment out only the defective locations from usable memory, preserving the majority of the memory capacity for continued use rather than discarding the entire module.
Solution Approach 2:
The patent recovers usable memory capacity by identifying and isolating only the defective locations through the defect table. Instead of discarding the entire memory module, the system recovers and continues to use all non-defective memory locations, maximizing the quantity of available memory resources.
3Loss of time
If memory defect tables are not maintained across reset cycles, then system startup is faster, but reliability deteriorates due to loss of defect information
Solution Approach 1:
The patent implements preliminary action by maintaining the defect table in non-volatile memory so that defect information persists across reset cycles. This allows the system to have defect information ready before operation begins, eliminating the need for re-detection during startup and maintaining reliability without startup time penalty.
Solution Approach 2:
The patent creates a persistent copy of the defect table in non-volatile memory that survives reset cycles. This copy preserves the defect information across system restarts, allowing the system to quickly restore reliable memory operation without re-detecting defects, thus balancing startup time and reliability.
Data Source
AI summary
Methods and apparatus for maintaining and utilizing system memory defect tables that store information identifying defective memory locations in memory modules. For some embodiments, the defect tables may be utilized to identify and re-map defective memory locations to non-defective replacement (spare) memory locations as an alternative to replacing an entire memory module. For some embodiments, some portion of the overall capacity of the memory module may be allocated for such replacement.