Processor Core Hardware Test Mode for Fault Detection
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Solution Overview
Problem
Existing technologies lack an efficient and reliable method for periodic hardware testing of processor cores to detect faults such as stuck-at or delay faults, while minimizing hardware modifications and ensuring availability for user applications.
Innovation Solution
A hardware test mode is implemented for a processor core, allowing for periodic testing by invoking a test mode that alters the microarchitectural state, enabling broad component coverage and fault detection. This is achieved through test mode registers that control the execution of test instructions and the allocation of physical registers, allowing for efficient detection of hardware faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardware test mode is implemented with minimal modifications, then device complexity is reduced, but testing reliability and fault detection capability are improved
Solution Approach 1:
The processor core performs self-testing by executing test instructions internally without requiring external test equipment. The test mode circuitry uses existing processor resources (registers, execution units) to conduct self-diagnostics, eliminating the need for complex external testing infrastructure while maintaining high fault detection capability
Solution Approach 2:
Existing processor components are made multi-functional by enabling them to operate in both normal processing mode and test mode. The same execution units, registers, and data paths used for regular computation are repurposed for hardware testing when test mode is activated, minimizing additional hardware modifications while achieving comprehensive fault detection
2Reliability
If periodic testing is performed frequently, then fault detection reliability is improved, but system availability for user applications deteriorates
Solution Approach 1:
The system implements periodic hardware testing at predetermined time intervals rather than continuously. A timer or counter triggers test mode activation at scheduled intervals, allowing the processor to alternate between normal operation and self-testing. This periodic approach ensures reliable fault detection while maintaining system availability for user applications during non-test periods
Solution Approach 2:
The test mode activation is made dynamic and configurable rather than static. The testing frequency and duration can be adjusted based on system state, allowing flexible balancing between reliability monitoring and application performance. The system can adaptively schedule tests during low-utilization periods to minimize impact on user applications
3Reliability
If comprehensive test coverage is achieved, then fault detection capability is improved, but testing time and system performance deteriorate
Solution Approach 1:
The testing mechanism implements targeted test instruction sequences that focus on exercising specific hardware components and pathways rather than exhaustive comprehensive testing. By selecting representative test cases that cover critical fault modes (stuck-at faults, delay faults) without testing every possible state, the system achieves sufficient fault detection capability with minimal testing time and performance impact
Data Source
AI summary
Systems and methods are disclosed for implementing a hardware test mode for a processor core. For example, some methods may include writing to one or more test mode registers to change a microarchitectural state of a processor core from a first state to one or more test mode states; executing a sequence of instructions on the processor core in the one or more test mode states to obtain a resulting architectural state of the processor core; comparing the resulting architectural state to an expected architectural state associated with the sequence of instructions to obtain a test result; and writing to the one or more test mode registers to restore the microarchitectural state of the processor core to the first state.