Cache Memory Debugging via Address Conversion and Display
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Solution Overview
Problem
Debugging computer programs for multiprocessor systems that maintain cache coherency is challenging due to the complexity of hardware configurations and the increased possibility of bug generation, making it difficult to analyze data stored in cache memories effectively.
Innovation Solution
A debugging system that includes an inputting unit for designation address information, a cache memory configuration information inputting unit, an address converter, a cache memory reading unit with a decoder, comparator, and reader, and a display unit to convert and compare tag addresses and index addresses, allowing for the display of data from the cache memory, thereby simplifying the analysis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a debugger displays cache memory data in order of index addresses, then the cache memory structure is preserved, but it becomes difficult to know the relation between cache data and main memory address
Solution Approach 1:
The patent introduces a new display dimension by showing both the index address order (original cache structure) and the corresponding main memory address relationship simultaneously. This allows debuggers to preserve the cache memory structure while also revealing the mapping relationship to main memory addresses, solving the information loss problem without compromising the original display organization.
2Reliability
If hardware is installed to keep coherency among cache memories, then coherency is maintained, but the configuration and control become complicated
Solution Approach 1:
The patent uses software simulation to replicate the functionality of hardware coherency management. By implementing coherency checking and maintenance through program execution rather than dedicated hardware circuits, the system achieves reliable cache coherency while avoiding the complexity of additional hardware configuration and control logic.
3Device complexity
If coherency function is provided in computer program, then hardware configuration is simplified, but possibility of bug generation increases
Solution Approach 1:
The patent introduces a debugging system as an intermediary that monitors and verifies the coherency maintenance function implemented in the computer program. This intermediary debugging capability allows the system to simplify hardware configuration while providing mechanisms to detect and prevent bugs in the software-based coherency management, thereby maintaining reliability.
4Device complexity
If simple cache mapping schemes are used, then circuit size and power consumption are reduced, but debugging analysis becomes more difficult
Solution Approach 1:
The patent creates a virtual representation of the cache memory mapping relationships through the debugging system. By copying and displaying the mapping information between simple cache mapping schemes and main memory addresses in a readable format, the system maintains the simplicity of the hardware circuit while providing comprehensive debugging capabilities that make analysis easier.
Data Source
AI summary
First tag addresses and data are stored in association with first index addresses in a memory cell unit provided in a cache memory. The first tag addresses and the first index addresses are configured based on address information respectively. Designation address information is provided to designate an address to read one of the stored data. The designation address information is converted to a second index address and second tag address by an address converter, in order to read the one of the stored data according to the designation address information. The memory cell unit is accessed according to the obtained second index address. When one of the first tag addresses matches the second tag address, the one of the data corresponding to the one of the first tag addresses is read. The designation address information and the one of the data are displayed in a cache memory display unit.