Low-Power Content-Addressable Memory via Sub-Array Segmentation
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Solution Overview
Problem
Content-addressable-memory (CAM) devices face challenges with high power consumption and manufacturing cost due to complex architecture and sensitivity to dust, leading to low manufacturing yield and high bit prices, especially in large capacity applications.
Innovation Solution
The implementation of a CAM device with multiple sub-arrays and redundant priority encoders allows for parallel comparison and defect remediation, reducing power consumption and improving manufacturing yield by controlling sub-array activation and using software and hardware repair mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large capacity CAM device is implemented with complex architecture, then the search functionality and capacity are improved, but power consumption increases and manufacturing yield decreases
Solution Approach 1:
The CAM device is divided into multiple sub-arrays (first sub-array, second sub-array, etc.) that can be independently activated. Only the sub-array containing the target data sequence is activated during search operations, reducing overall power consumption while maintaining large capacity. This segmentation allows the system to scale capacity without proportionally increasing power consumption.
2Quantity of substance
If a large capacity CAM device is implemented with complex architecture, then the search functionality and capacity are improved, but manufacturing yield decreases due to sensitivity to dust
Solution Approach 1:
Dividing the CAM into multiple sub-arrays reduces the complexity of each individual sub-array, making them less sensitive to manufacturing defects and dust particles. Each sub-array can be independently tested and repaired, improving overall manufacturing yield.
Solution Approach 2:
Redundant priority encoders are provided for each sub-array to compensate for potential defects. If a defect is detected in a priority encoder, the redundant unit can take over, ensuring continuous operation and improving manufacturing yield by providing built-in fault tolerance.
3Ease of repair
If multiple sub-arrays are implemented with redundant priority encoders, then defect remediation capability is improved, but device complexity increases
Solution Approach 1:
Each sub-array has its own dedicated redundant priority encoder, allowing defect remediation to be localized to specific sub-arrays rather than requiring system-wide complexity. This modular approach improves ease of repair while controlling overall device complexity.
Solution Approach 2:
Redundant priority encoders are strategically placed at specific locations (local quality) within each sub-array rather than uniformly distributed throughout the entire CAM device. This allows defect remediation capability to be provided where needed while minimizing overall device complexity.
4Use of energy by moving object
If sub-array activation control is implemented, then power consumption is reduced, but control mechanism complexity increases
Solution Approach 1:
The control mechanism is segmented to activate only specific sub-arrays based on the search key, rather than activating the entire CAM device. This reduces power consumption by keeping inactive sub-arrays in a low-power state while maintaining relatively simple control logic.
Solution Approach 2:
Sub-arrays are pre-configured and organized so that the activation control mechanism can quickly determine which sub-array to activate based on the search key. This preliminary organization reduces the complexity of real-time control decisions while achieving power consumption reduction.
Data Source
AI summary
A plurality of content-addressable-memory sub-arrays simultaneously performs a parallel comparison between data sequences arranged in a row direction of memory cells and a search data sequence input from outside, and outputs a result of the comparison for each data sequence. A first input pin receives an input of the search data sequence. A second input pin receives an input of a search data sequence arbitrarily designating a content-addressable-memory sub-array. Each of the content-addressable-memory sub-arrays includes an activation control unit that controls activation of the content-addressable-memory sub-arrays based on the search data sequence.