Hash-Based TCAM Read Selection Using Storage Activity
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Solution Overview
Problem
Ternary Content Addressable Memory (TCAM) systems require significant resources due to the need to compare each data value with a key in parallel, leading to inefficiencies in resource utilization.
Innovation Solution
The implementation of a hash-based TCAM system that uses a hash index to determine a common memory address shared by multiple memory devices and a storage activity index to identify which devices store current content data, reducing the number of devices accessed during a search operation by only searching those with active data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel comparison of each data value with key is used in TCAM, then content search capability is achieved, but resource consumption increases significantly
Solution Approach 1:
The patent divides the TCAM into multiple banks, where each bank stores a portion of the content data. Instead of comparing all data values across the entire TCAM in parallel, the hash function segments the search space by directing comparisons to specific banks based on the hash value of the search key. This segmentation reduces the number of parallel comparisons needed while maintaining complete content search capability.
Solution Approach 2:
The patent introduces a hash function as an intermediary between the search key and the content data comparison process. The hash function processes the search key to generate a hash value that serves as an index, directing the search to specific memory locations or banks. This intermediary eliminates the need for exhaustive parallel comparison across all TCAM entries, significantly reducing resource consumption while preserving search accuracy.
2Reliability
If all memory devices are accessed during search operation, then complete content search is performed, but energy consumption and heat buildup increase
Solution Approach 1:
The patent performs preliminary action by computing the hash value of the search key before accessing memory devices. This hash value pre-determines which specific memory locations or banks contain the relevant content data. By performing this preliminary hashing step, the system avoids unnecessary access to memory devices that do not contain matching data, thereby reducing energy consumption and heat buildup while ensuring complete content search.
3Speed
If multiple memory devices are simultaneously accessed, then parallel search speed is improved, but device complexity increases
Solution Approach 1:
The patent segments the TCAM into multiple independently accessible banks, each handling a specific portion of the content data. The hash function determines which segmented banks need to be accessed for a given search key. This segmentation enables selective parallel access to only the relevant banks, improving search speed while avoiding the complexity of coordinating simultaneous access across all memory devices.
Solution Approach 2:
The patent applies local quality by making different banks or memory locations have specialized roles based on their content. Each bank is optimized for storing specific types or ranges of content data, and the hash function directs searches to the appropriate bank with local expertise. This local specialization improves search efficiency and reduces the complexity of managing uniform access across all devices.
Data Source
AI summary
A method is provided to control a content addressable memory that includes multiple integrated circuit memory devices that include common memory address locations and that are coupled for simultaneous access to the common memory address locations, the method comprising; determining a hash value, based upon a received key value, that corresponds to a common memory address location of the multiple memory devices; providing activity status information for multiple common memory address locations of the memory devices; selecting a memory devices from which to output stored content data from the corresponding common memory address location, based upon storage activity status information; and causing the selected one or more memory devices to output stored content data.