ECC Status Encoding for DRAM Memory Channel Exceptions
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Solution Overview
Problem
Existing low latency, high bandwidth, high capacity DIMM-based DRAM systems lack an efficient means of returning precise exception or status information to the host system, leading to excessive memory channel resource consumption and complex flow control requirements, especially as they evolve to include heterogeneous memory types and increased local control.
Innovation Solution
A method that encodes status conditions using error correction codes, allowing for in-band status signaling without additional signal lines or increased codeword size, by transforming checksums based on status conditions and using inverse transformations to recover original data, leveraging techniques like Hamming, BCH, or Reed-Solomon encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If status polling is used to return exception condition information to the host system, then status information can be communicated, but memory channel resources are excessively consumed
Solution Approach 1:
The patent merges status information communication with error correction code transmission by encoding status conditions within the ECC codeword structure. This allows status information to be conveyed alongside data without requiring separate communication channels or additional polling transactions, thereby eliminating the excessive memory channel resource consumption associated with traditional status polling methods.
Solution Approach 2:
The error correction code structure is given multi-functionality by enabling it to carry both error correction information and status condition information. The ECC codeword serves dual purposes: maintaining data integrity through error correction while simultaneously communicating exception conditions or status information back to the host system, thus eliminating the need for dedicated status communication resources.
2Loss of information
If interrupt-based signals are used to return status information, then exception conditions can be communicated, but multiple transactions with complex flow control are required
Solution Approach 1:
The patent combines exception condition communication with the existing data transfer protocol by embedding status information within the ECC codeword. This eliminates the need for separate interrupt-based signal transactions and their associated complex flow control mechanisms, as status information is conveyed in-band alongside normal data operations.
Solution Approach 2:
The patent extracts status condition information from the traditional interrupt signal path and integrates it into the data transmission channel. By taking out the status communication function from the complex interrupt handling mechanism and embedding it within the ECC structure, the system eliminates multiple transactions and simplifies flow control requirements.
3Loss of information
If additional signal lines are added to communicate status information, then status communication capability is improved, but device complexity and resource usage increase
Solution Approach 1:
The existing ECC signal lines are given multi-functionality to carry both error correction data and status information. By making the existing communication infrastructure universal, the patent enables status communication without adding any additional signal lines, thereby maintaining device complexity at current levels while improving status communication capability.
Solution Approach 2:
The patent merges status information with error correction code data, allowing both types of information to be transmitted through the same signal lines. This consolidation eliminates the need for separate dedicated status signal lines, as status information is combined with the existing ECC transmission channel.
4Measurement precision
If codeword size is increased to encode status information, then status communication precision is improved, but bandwidth efficiency decreases
Solution Approach 1:
The patent enables the existing codeword structure to serve multiple functions simultaneously - maintaining error correction capabilities while encoding status information within the same codeword bits. This multi-functionality allows precise status communication without increasing codeword size, as status information is embedded within the existing code structure rather than adding separate status fields.
Solution Approach 2:
The patent combines status information encoding with error correction coding by utilizing the existing redundancy bits in the ECC structure. By merging status communication with error correction functionality, the system achieves precise status information transmission without increasing overall codeword size or reducing bandwidth efficiency.
Data Source
AI summary
A status encoder generates a checksum that encodes a status condition together with the checksum of an associated message. A receiver determines an inverse transformation that when applied to the received status-encoded checksum recovers the parity information associated with the codeword. The status condition can then be recovered based on the selection of the inverse transformation that correctly recovers the parity information from the status-encoded checksum. Beneficially, the status condition can be encoded without requiring additional signal lines or lengthening the codeword relative to conventional error correction devices.