Processor Scan Testing Bypassing Defective Exchange Paths
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Solution Overview
Problem
In processor repair scenarios, scan tests can fail due to inclusion of defective exchange paths and processing units, even after repair, leading to inaccurate assessment of chip functionality.
Innovation Solution
A method and system that enable a scan test to bypass repaired-out processing units and defective exchange paths by switching in repair processing units and using exchange path functional testing to identify and exclude defective components, ensuring that only functional paths are used in subsequent scan tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scan testing is performed on a repaired chip including defective processing units and exchange paths, then the scan test coverage is comprehensive, but the scan test fails due to defective components
Solution Approach 1:
The scan chain is segmented into multiple independent scan chains, each associated with a specific processing unit or exchange path. This allows selective activation of only functional scan chains during testing, excluding those associated with repaired-out defective components, thereby preventing test failures while maintaining coverage of operational circuitry.
Solution Approach 2:
The scan chain configuration is made dynamic and reconfigurable based on the operational status of processing units and exchange paths. Functional scan chains are activated while defective ones are deactivated, allowing the test system to adapt to the repaired chip state and achieve both comprehensive coverage and high success rate.
2Measurement precision
If all processing units are included in scan testing, then complete fault detection is achieved, but defective processing units cause false failures
Solution Approach 1:
Before performing scan testing, the system preliminarily identifies which processing units and exchange paths are functional and which are defective. Based on this preliminary assessment, the scan chains are pre-configured to include only functional components, ensuring that subsequent testing achieves both complete fault detection and accurate results without false failures from defective units.
3Ease of operation
If exchange paths are used for data transmission in repaired chips, then functional operation is restored, but defective exchange paths cause scan test failures
Solution Approach 1:
The exchange fabric is segmented into multiple exchange paths, each with its own scan chain. During scan testing, only exchange paths associated with functional processing units are activated. This segmentation allows the system to maintain functional operation through available paths while excluding defective paths from testing, preventing false failures.
Data Source
AI summary
A method for repairing a processor. The processor comprises a plurality of processing units and an exchange comprising a plurality of exchange paths for transmitting data between the processing units. Each processing unit is connected to output data to a respective exchange path. An exchange path functional test of at least a portion of the exchange paths is carried out. Based on the exchange path functional test, it is identified that one or more of the exchange paths is defective, and the processing units connected to the one or more defective exchange paths is identified. The identified processing units are switched out of functional operation of the processor and switching in at least one repair processing unit connected to a non-defective exchange path for functional operation of the processor.