TCAM Sub-Block Presearch for Lower-Power Memory Search
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Solution Overview
Problem
Ternary Content Addressable Memory (TCAM) devices face challenges in achieving low power consumption while maintaining performance, particularly due to the complexity of managing 'Don't Care' states in TCAM cells and the resulting increased power consumption during searches.
Innovation Solution
The semiconductor device incorporates sub-blocks with memory arrays and sub-search units that generate flag data to pre-search and compare with input data, allowing for efficient search operations and reducing unnecessary power consumption by selectively activating search lines based on comparison results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If TCAM cells with 'Don't Care' states are used to increase storage capacity and search flexibility, then the adaptability and storage capacity are improved, but the power consumption increases due to search current generation
Solution Approach 1:
The TCAM array is divided into multiple sub-blocks, each with its own sub-search unit. This segmentation allows selective activation of only those sub-blocks that contain valid data matching the search criteria, rather than searching the entire array. The flag data generation part creates indicator data for each sub-block, enabling the search unit to identify and activate only relevant segments, thus reducing overall power consumption while maintaining the ability to handle 'Don't Care' states.
Solution Approach 2:
Flag data is generated in advance for each sub-block based on the stored data, indicating whether each sub-block contains valid data that could match the search criteria. This preliminary action allows the search unit to pre-screen sub-blocks before performing the actual search operation, avoiding unnecessary search current generation in sub-blocks with no valid data, thereby reducing power consumption while preserving search flexibility.
2Use of energy by moving object
If block selection signals are used to narrow down search blocks and reduce power consumption, then the power consumption is reduced, but the device complexity increases due to the need for selection signals and control logic
Solution Approach 1:
The flag data generation function and the search function are merged into an integrated search system. The flag data is generated automatically as part of the data storage process, and the search unit uses this flag data seamlessly during search operations. This merging eliminates the need for separate complex control logic to manage block selection, as the flag data automatically guides the search process, thereby reducing device complexity while maintaining power consumption benefits.
Solution Approach 2:
The system uses its own stored data to automatically generate flag data that indicates which sub-blocks contain valid data. This self-service mechanism eliminates the need for external block selection signals or complex control logic, as the flag data generated from the stored data itself directs the search process. The system effectively manages its own search optimization without additional control complexity.
3Reliability
If power is supplied to all memory areas to ensure data access, then the reliability and access speed are improved, but the power consumption increases
Solution Approach 1:
The power supply to memory areas is made dynamic rather than static. Sub-blocks are activated only when needed, based on the search criteria and the flag data indicating which sub-blocks contain valid data. This dynamic power management ensures that power is supplied to the minimum necessary areas to maintain search reliability, while avoiding continuous power supply to all areas, thereby reducing overall power consumption while preserving data access reliability.
Solution Approach 2:
Different power supply conditions are applied to different sub-blocks based on their individual characteristics and content. Sub-blocks containing valid data are supplied with power when needed, while sub-blocks with no valid data are kept in a low-power state. This local quality approach ensures that power is allocated according to the actual needs of each region, maintaining search reliability where necessary while reducing overall power consumption.
Data Source
AI summary
The present invention provides a semiconductor device that can reduce the power consumption. The semiconductor device includes a plurality of sub-blocks each including a memory cell array, and a plurality of sub-search units corresponding to the respective sub-blocks. Of the data stored in each row of the memory cell array, each sub-block searches for data that matches the input search data according to a search instruction, and outputs a search result indicating hit or miss for each row. Each sub-search unit includes a flag data generation part that generates flag data for presearch to compare with part of the input search data based on the data stored in the corresponding memory cell array, and a search part that compares part of the input search data with the flag data generated by the flag data generation part, and outputs the search instruction to the corresponding sub-block based on the comparison result.