Memory Controller Early Write Acknowledgement Latency
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Solution Overview
Problem
Chiplet systems face challenges in minimizing processor stall time due to delays in memory write operations, as existing technologies often wait for memory write commands to be completed before acknowledging them, leading to increased latency and reduced performance.
Innovation Solution
Implementing a memory controller chiplet that returns a write acknowledgement once the write command has been selected for processing by the input multiplexor, rather than waiting for the write to be completed, thereby preserving the ordering of requests and allowing the processor to continue operations sooner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory controller waits for memory write commands to be completed before acknowledging them, then data integrity is ensured, but processor stall time increases and performance decreases
Solution Approach 1:
The memory controller sends an acknowledgement to the processor before the memory write operation is actually completed. Specifically, the controller acknowledges the write command after receiving it and before the data is fully written to the memory device, allowing the processor to continue executing instructions without waiting for the complete write operation.
Solution Approach 2:
The memory write operation is divided into distinct phases: (1) receiving the write command from the processor, (2) sending an acknowledgement to the processor, and (3) completing the actual data write to memory. This segmentation allows the acknowledgement phase to proceed independently of the data transfer phase, reducing processor stall time while maintaining data integrity through proper ordering enforcement.
2Loss of time
If the memory controller returns write acknowledgement early (before completion), then processor stall time is reduced, but request ordering may be compromised
Solution Approach 1:
The memory controller implements a feedback mechanism that tracks the status of outstanding write operations and enforces ordering constraints. When an early acknowledgement is sent, the controller maintains internal state information about the write command and ensures that subsequent write operations are processed in the correct order, preventing ordering violations despite early acknowledgements.
Solution Approach 2:
The controller performs preliminary validation and ordering checks before sending the early acknowledgement. By verifying that the write command adheres to ordering constraints prior to sending the acknowledgement, the controller ensures that request ordering is maintained even though the acknowledgement is sent before the actual write completion.
Data Source
AI summary
Disclosed in some examples are methods, systems, memory controllers, devices, and machine-readable mediums which minimize this stall time by returning a memory write acknowledgement once a write command has been selected by the memory controller input multiplexor rather than when the memory write command has been performed. Because the memory controller enforces an ordering to memory once the packet has been selected at an input multiplexor, ordering of prior and subsequent requests to the same address location are preserved and providing the response early allows the processor to continue its operations earlier without any harmful effects.