NAND Flash Content Addressable Memory for Parallel Key Search
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Solution Overview
Problem
Conventional memory technologies face inefficiencies in data retrieval and storage due to their address-based retrieval methods, which limit parallel processing and increase power consumption and latency, especially in large-scale data searches.
Innovation Solution
A content addressable memory (CAM) system based on NAND flash memory architecture, where keys are written along bit lines and searched using word lines, allowing for simultaneous comparison of multiple keys and reduced power consumption through on-chip processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional address-based memory retrieval is used, then data can be located at a specified address, but parallel processing is limited and latency increases for large-scale data searches
Solution Approach 1:
The patent replaces the mechanical address-based sequential access mechanism with a content-based parallel comparison mechanism. Instead of physically navigating to an address, the system broadcasts the search key to all memory locations simultaneously, and matching locations automatically respond. This substitution of the access mechanism enables parallel processing of multiple keys and dramatically reduces search latency.
Solution Approach 2:
The patent transitions from one-dimensional address-based access to multi-dimensional content-based access. By encoding search keys across multiple bit lines and using word lines for parallel comparison, the system creates a dimensional framework where all memory locations can be accessed simultaneously through content matching rather than sequential address traversal.
2Ease of operation
If conventional memory retrieval methods are used, then data access is straightforward, but power consumption increases due to sequential access operations
Solution Approach 1:
The patent replaces the power-intensive sequential access mechanism with a content-based parallel comparison mechanism. The system broadcasts the search key to all memory locations simultaneously, and only matching locations activate their output transistors. This substitution eliminates the need for sequential word line activation and reduces overall power consumption while maintaining ease of operation through automatic matching.
Solution Approach 2:
The memory system performs automatic content matching without requiring external control logic for each comparison operation. When the search key is broadcast, matching memory locations self-activate their output transistors to indicate a match, eliminating the need for complex external control circuits and reducing power consumption associated with control logic operations.
3Adaptability or versatility
If content addressable memory is implemented using conventional memory with CPU search, then data retrieval can be flexible, but device complexity and processing overhead increase
Solution Approach 1:
The patent merges the memory storage function with the content comparison function into a single integrated structure. The memory cells themselves perform the comparison operation by naturally responding to matching search keys, eliminating the need for separate CPU-based search logic. This merging reduces system complexity while maintaining search flexibility.
Solution Approach 2:
The memory system performs automatic content matching without requiring external control logic for each comparison operation. When the search key is broadcast, matching memory locations self-activate their output transistors to indicate a match, eliminating the need for complex external control circuits and reducing system complexity.
4Quantity of substance
If large key sizes are required for content addressable memory, then more data can be stored and searched, but conventional CAM architectures become impractical
Solution Approach 1:
The patent transitions from one-dimensional address-based access to multi-dimensional content-based access. By encoding search keys across multiple bit lines and using word lines for parallel comparison, the system creates a dimensional framework where all memory locations can be accessed simultaneously through content matching rather than sequential address traversal.
Solution Approach 2:
The patent segments the key data across multiple bit lines within the memory array. Instead of requiring a single large comparator, the key is divided and distributed across multiple memory locations, with each location comparing a portion of the key. This segmentation enables support for large key sizes while maintaining architectural simplicity and feasibility.
Data Source
AI summary
A NAND Flash based content addressable memory (CAM) is used for a key-value addressed storage drive. The device can use a standard transport protocol such as PCI-E, SAS, SATA, eMMC, SCSI, and so on. A host writes a key-value pair to the drive, where the drive writes the keys along bit lines of a CAM NAND portion of the drive and stores the value in the drive. The drive then maintains a table linking the keys to location of the value. In a read process, the host provides a key to drive, which then broadcasts down the word lines of blocks storing the keys. Based on any matching bit lines, the tables can then be used to retrieve and supply the corresponding data to the host.