Content Addressable Memory Error Detection via Dual-Group Comparison
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Solution Overview
Problem
As semiconductor memory devices shrink, the soft error rate increases, leading to bit value changes due to external energy, causing multiple hit errors in content addressable memory (CAM), necessitating effective error detection while minimizing power consumption for portable devices.
Innovation Solution
Implementing a content addressable memory (CAM) device with a primary group of memory cells and a secondary group storing identical data, where searches are performed only on the primary group, and bits are concurrently compared to the secondary group to detect and correct single bit errors without discharging the entire CAM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error detection is implemented in CAM devices, then reliability is improved, but power consumption increases
Solution Approach 1:
The CAM device is divided into a primary CAM portion and a secondary CAM portion, each storing copies of data. Error detection is performed by comparing results from both portions, segmenting the detection function to reduce power consumption compared to checking every bit in the entire CAM device.
Solution Approach 2:
A secondary copy of the CAM data is maintained in a separate portion of the CAM device. This copy is used for error detection through comparison with the primary data, enabling error detection without repeatedly accessing and consuming power on the same data bits.
2Volume of moving object
If CAM geometry is shrunk to reduce device size, then device dimensions are improved, but soft error rate increases
Solution Approach 1:
Data is copied to a secondary CAM portion, creating redundancy that allows error detection. This copying mechanism compensates for the increased soft error rate caused by smaller geometries, maintaining reliability despite size reduction.
Solution Approach 2:
The comparison circuitry provides feedback by comparing data from the primary and secondary CAM portions. When discrepancies are detected, the system can identify and correct errors, creating a feedback loop that maintains reliability in shrunk geometries.
Data Source
AI summary
A content addressable memory (CAM) includes a first entry which includes one or more bits, a second entry which includes one or more bits, first comparison circuitry configured to compare each bit of a comparand to a corresponding bit of the one or more bits of the first entry and to provide a hit/miss indicator in response thereto, and second comparison circuitry configured to compare each bit of the one or more bits of the first entry to a corresponding bit of the one or more bits of the second entry and to provide a fault indicator in response thereto.