AMB Spare Memory Rerouting for DRAM Defect Repair
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Solution Overview
Problem
Existing memory modules require expensive and time-consuming re-work to replace defective memory chips, especially when only single-bit errors are detected, which increases manufacturing costs and reduces efficiency.
Innovation Solution
Integrating a spare memory within the Advanced Memory Buffer (AMB) of fully-buffered memory modules, allowing the AMB to reroute memory access to the spare memory when defective addresses are detected, thereby eliminating the need for re-soldering and reducing pre-screening costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory chips are extensively pre-screened to detect single-bit errors, then manufacturing reliability improves, but manufacturing cost and time increase
Solution Approach 1:
The patent implements preliminary action by performing extensive pre-screening tests during manufacturing to detect single-bit errors in memory chips before final assembly. This allows defective chips to be identified and replaced with spare chips while the module is still being manufactured, preventing field failures and eliminating the need for costly post-manufacturing rework.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating spare memory chips into the module design during manufacturing. These spare chips serve as a buffer against potential defects, allowing the system to compensate for failures without requiring rework. The spare chips are activated only when defects are detected, providing a safety net that maintains productivity while ensuring reliability.
2Reliability
If defective memory chips are replaced through re-soldering, then module reliability improves, but manufacturing cost and time increase
Solution Approach 1:
The patent applies preliminary action by identifying and replacing defective memory chips during the manufacturing process itself, rather than allowing defects to persist to the field. By performing chip replacement while the module is on the assembly line, the patent eliminates the need for complex post-manufacturing rework operations and ensures modules leave the factory in working condition.
Solution Approach 2:
The patent uses spare memory chips as intermediaries to replace defective chips. Rather than directly repairing the defective chip through complex rework operations, the system introduces a functional spare chip as a substitute, which is then activated to replace the defective chip's function. This intermediary approach simplifies the manufacturing process while ensuring module reliability.
3Productivity
If limited pre-screening is performed to reduce costs, then manufacturing efficiency improves, but defect detection capability worsens
Solution Approach 1:
The patent implements preliminary action by performing comprehensive pre-screening tests during the manufacturing process to detect single-bit errors in memory chips. This extensive testing is conducted before final assembly, allowing defective chips to be identified and replaced with spare chips while the module is still being manufactured, thereby maintaining both detection accuracy and manufacturing efficiency.
Solution Approach 2:
The patent applies parameter changes by modifying the testing parameters during the pre-screening process to specifically detect single-bit errors. By adjusting test patterns and parameters to target single-bit error detection, the system achieves high defect detection accuracy without requiring excessively lengthy test sequences, thus maintaining manufacturing efficiency while improving measurement precision.
Data Source
AI summary
A repairing fully-buffered memory module can have memory chips with some defects such as single-bit errors. A repair controller is added to the Advanced Memory Buffer (AMB) on the memory module. The AMB fully buffers memory requests that are sent as serial packets over southbound lanes from a host. Memory-access addresses are extracted from the serial packets by the AMB. The repair controller compares the memory-access addresses to repair addresses and diverts access from defective memory chips to a spare memory for the repair addresses. The repair addresses can be located during testing of the memory module and programmed into a repair address buffer on the AMB. The repair addresses could be first programmed into a serial-presence-detect electrically-erasable programmable read-only memory (SPD-EEPROM) on the memory module, and then copied to the repair address buffer on the AMB during power-up.