Internal State Checksum Circuitry for Processor Diagnostics
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Solution Overview
Problem
Conventional diagnostic methods struggle to efficiently cover and probe internal state in data processing apparatuses, particularly micro-architectural state, which is hard to reach and increases development time and overhead in software test libraries.
Innovation Solution
Incorporating checksum generating circuitry to derive and expose a checksum based on internal state, accessible by diagnostic control agents, allowing selective probing of hard-to-reach state without significant additional circuit overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional diagnostic methods are used to probe internal state, then diagnostic coverage is limited, but software test library size and development time increase significantly
Solution Approach 1:
The patent extracts the checksum generation function from the main processing circuitry and implements it as separate checksum generating circuitry. This extracted component can be selectively activated to generate checksums for diagnostic purposes without affecting normal processing, thereby improving diagnostic coverage while minimizing impact on development time
Solution Approach 2:
The patent introduces checksums as an intermediary representation of internal state. Instead of directly probing complex internal state, the diagnostic control agent obtains checksums that mediate the diagnostic process, making it more efficient and reducing the overhead in software test libraries
2Measurement precision
If software test libraries are expanded to cover more internal state, then diagnostic coverage improves, but test library size and complexity increase
Solution Approach 1:
The patent extracts the checksum generation functionality into dedicated hardware circuitry, removing the burden from software test libraries. This allows comprehensive diagnostic coverage to be achieved through hardware-based checksum generation rather than expanding complex software test sequences
Solution Approach 2:
The patent replaces mechanical/software-based state probing with a hardware-based checksum generation system. This substitution eliminates the need for large software test libraries while maintaining or improving diagnostic coverage, as the checksum generating circuitry automatically computes state verification values
3Measurement precision
If checksum generating circuitry is added to expose internal state, then diagnostic coverage improves, but circuit overhead increases
Solution Approach 1:
The checksum generating circuitry is designed to be universally applicable to multiple internal state elements. A single checksum generator can compute checksums for different cache lines, buffer states, or other internal elements by receiving their respective state data, thereby providing comprehensive diagnostic coverage without proportionally increasing circuit overhead
Solution Approach 2:
The checksum generating circuitry can be selectively activated and deactivated. During normal operation, the checksum generator remains inactive to minimize overhead, and is only activated when diagnostic information is needed, effectively discarding its overhead during non-diagnostic periods and recovering it when needed
Data Source
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AI summary
An apparatus has processing circuitry 2 to perform data processing in response to instructions; at least one control storage element 74 to store internal state for controlling operation of the processing circuitry; and checksum generating circuitry 70 to generate a checksum based on at least one item of internal state stored in the at least one control storage element 74. The checksum is stored in a diagnostic storage location 72 from which information is accessible to a diagnostic control agent (e.g. software executing on the processing circuitry and/or an external device). This makes design of software test libraries for detecting hardware faults much more efficient.