TCAM False Hit Detection via Single-Port Memory Copy
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Solution Overview
Problem
Ternary content-addressable memory (TCAM) devices are prone to soft errors due to radiation, leading to false hits during search operations, which can cause misrouting of packets and delays in network systems, and existing error detection and correction techniques are not compatible with TCAM.
Innovation Solution
A memory apparatus comprising a TCAM coupled with single-port memories, a TCAM controller that compares search tags with data entries from both the TCAM and memories to detect false hits, and correct errors by reconfiguring the TCAM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If TCAM is used to enable fast search operations with don't care bits, then search speed and flexibility are improved, but reliability deteriorates due to soft errors from radiation
Solution Approach 1:
The patent creates a copy of the TCAM in the form of a single-port memory that stores the same data entries. This copy is used to verify search results by comparing the TCAM output against the memory output, thereby detecting soft errors without affecting the fast search performance of the original TCAM
Solution Approach 2:
The patent implements a feedback mechanism where the single-port memory continuously monitors and compares search results against stored reference data. When a discrepancy is detected (indicating a soft error), the system generates feedback signals to correct the TCAM output or trigger error handling procedures
2Productivity
If TCAM is used to achieve single-clock-cycle search operations, then productivity is improved, but device complexity increases due to additional comparison circuitry
Solution Approach 1:
Instead of adding complex comparison circuitry to the TCAM itself, the patent creates a simpler single-port memory copy that stores the same data entries. This copy is accessed during search operations to verify results, avoiding the need for additional complex comparison logic within the TCAM structure
Solution Approach 2:
The single-port memory acts as an intermediary verification mechanism between the TCAM search operation and the final result validation. It simplifies the overall system by providing a straightforward memory-based comparison approach rather than requiring complex integrated comparison circuitry
3Productivity
If TCAM is used to perform search-intensive tasks, then productivity is improved, but power dissipation increases since every comparison circuit is active on every clock cycle
Solution Approach 1:
The single-port memory is accessed periodically during search operations rather than continuously. The memory is read only when needed to verify search results, allowing it to remain inactive during normal TCAM operation and thus reducing overall power dissipation while maintaining verification capability
Data Source
AI summary
A memory apparatus for detecting false hits in a content-addressable memory (CAM) is disclosed. The memory apparatus includes a controller coupled to the CAM and a memory. The controller receives a search result including an address from the CAM, the address corresponding to a matching entry from a first set of data entries that matches a search tag. The controller provides a read address based on the address to the memory, which returns a second data entry from a second set of data entries corresponding to the read address. The controller receives the read data and generates an error detection result based on a comparison between the second data entry and the search tag.