Cache Memory Write Control for Partial RMW and ECC Updates
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Solution Overview
Problem
Existing memory systems face inefficiencies in managing read-modify-write operations, particularly in partial writes, leading to increased processing time and power consumption due to the need for additional read and write transactions.
Innovation Solution
Implementing a read-modify-write (RMW) memory pipeline that performs partial writes by reading conforming data from the cache memory, correcting errors, and generating new error correction codes (ECC) to ensure data integrity before writing, thereby reducing the number of memory transactions required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional memory write operations are used for partial writes, then data can be written to cache memory, but additional read and write transactions are required increasing processing time and power consumption
Solution Approach 1:
The patent segments the cache line into multiple chunks, allowing the memory pipeline to identify and process only the specific chunk that needs to be written. This segmentation enables partial writes without requiring full read-modify-write cycles for entire cache lines, thereby reducing processing time and transaction overhead.
Solution Approach 2:
The patent implements partial write operations where only the necessary portion of a cache line (one chunk) is written instead of performing complete read-modify-write cycles on entire cache lines. This partial action approach reduces the number of memory transactions required, improving productivity while minimizing time loss.
2Productivity
If traditional memory write operations are used for partial writes, then data can be written to cache memory, but additional read and write transactions are required increasing power consumption
Solution Approach 1:
By segmenting the cache line into chunks and enabling identification of the specific chunk to be written, the system avoids unnecessary read and write transactions for other chunks. This segmentation strategy reduces the number of active transactions, thereby lowering power consumption while maintaining operational efficiency.
Solution Approach 2:
The partial write capability allows the system to perform only the necessary write operation on the specific chunk without initiating full read-modify-write sequences. This reduction in transaction scope directly decreases power consumption while preserving productivity.
3Reliability
If read-modify-write operations are performed for every write, then data integrity can be maintained, but the number of transactions increases reducing system performance
Solution Approach 1:
The patent segments cache lines into chunks and implements chunk-level addressing, allowing the memory pipeline to perform read-modify-write operations only on the specific chunk that needs updating. This selective approach maintains data integrity for the modified chunk while avoiding unnecessary transactions on other chunks, thus preserving system performance.
Solution Approach 2:
By implementing partial write operations on specific chunks rather than entire cache lines, the system maintains data integrity where needed while reducing the overall number of transactions. This partial action strategy balances reliability requirements with performance optimization.
Data Source
AI summary
In described examples, a processor system includes a processor core that generates memory write requests, and a cache memory with a memory controller having a memory pipeline. The cache memory has cache lines of length L. The cache memory has a minimum write length that is less than a cache line length of the cache memory. The memory pipeline determines whether the data payload includes a first chunk and ECC syndrome that correspond to a partial write and are writable by a first cache write operation, and a second chunk and ECC syndrome that correspond to a full write operation that can be performed separately from the first cache write operation. The memory pipeline performs an RMW operation to store the first chunk and ECC syndrome in the cache memory, and performs the full write operation to store the second chunk and ECC syndrome in the cache memory.