Content Addressable Word Decoder Array for Low Power Memory Search
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Solution Overview
Problem
Existing content addressable memory (CAM) systems face challenges in achieving horizontal cascading due to difficulties in conveying match information between elements, resulting in high power consumption and cost, making them inefficient and expensive compared to random access memory (RAM).
Innovation Solution
A memory system utilizing a plurality of content addressable word decoders and memory cells, where each memory cell is associated with a programmable word decoder, allowing for CAM-like functionality with RAM efficiency and low cost by using traditional RAM cells and providing parallel search capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional CAM devices are used to achieve parallel search capabilities, then search speed is improved, but power consumption and cost increase significantly
Solution Approach 1:
The CAM device is divided into multiple independently operable banks, each capable of performing parallel comparisons. This segmentation allows the system to process multiple comparands simultaneously across different banks, maintaining high search speed while enabling selective activation of banks to reduce overall power consumption when full parallel processing is not required.
Solution Approach 2:
The CAM device implements dynamic power management by selectively enabling or disabling banks based on operational requirements. The system can transition between different operational modes, activating only the necessary number of banks for each search operation, thereby dynamically adjusting power consumption while maintaining search capability.
2Quantity of substance
If horizontal cascading of CAM elements is implemented to increase storage capacity, then memory capacity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The CAM device is organized into multiple banks that can be horizontally cascaded to increase total storage capacity. Each bank is an independent module with its own comparison logic and output registers, allowing capacities to be scaled by simply adding more banks without increasing the complexity of individual bank operations.
Solution Approach 2:
Multiple CAM banks are combined through a unified control interface and shared output logic. The banks operate in parallel but can be controlled as a single device, merging their individual capacities to achieve large total storage while maintaining manageable complexity through standardized interconnection protocols.
3Measurement precision
If multiple response outputs from CAM are accessed serially to resolve ambiguous addressing, then addressing accuracy is improved, but access time increases
Solution Approach 1:
The device transitions from serial to parallel access by providing multiple independent output registers, one for each bank. When multiple banks match a comparand, all matching results are presented simultaneously in parallel, eliminating the need for sequential access while maintaining the ability to distinguish multiple matches through their respective bank identifiers.
Solution Approach 2:
Bank identifier signals serve as intermediaries that accompany each match output. These identifiers allow the system to distinguish which bank produced each match result, enabling accurate addressing and selection among multiple matches without requiring sequential access to determine the source of each result.
Data Source
AI summary
A memory system according to one embodiment includes a plurality of content addressable word decoders, and memory cells associated with each of the word decoders. A memory system according to another embodiment includes a word decoder storing an identifier which is a subset of a memory address, the word decoder being responsive to a match of the identifier and an incoming subset of the memory address. A memory system according to yet another embodiment includes a word decoder having more than sixteen address line inputs. A memory system according to a further embodiment includes a word decoder array having fewer word decoders than combinations of memory addresses. Methods are also provided.