Row Buffer Auto-Precharge for Lower Memory Access Latency
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Solution Overview
Problem
In memory systems, speculative activation commands can lead to unnecessary latency and bandwidth overhead due to incorrect predictions, and read-only activations cause power consumption and latency issues when keeping pages open for extended periods.
Innovation Solution
The introduction of an 'activate with auto-precharge' (ACT+AP) command, which opens a page of memory cells, latches logic states, writes them back, and maintains power to the row buffer after closing the page, allowing for reduced latency, command traffic, and power consumption by combining activation and precharge operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If speculative activation commands are used to predict future memory access patterns, then access speed may be improved, but unnecessary latency and bandwidth overhead occur due to incorrect predictions
Solution Approach 1:
The memory device autonomously determines whether to precharge a row buffer without external intervention. After an activate command, the memory device monitors for subsequent read/write commands to the same row and automatically precharges the row buffer if no further accesses are detected within a threshold period, eliminating the need for the host to issue unnecessary precharge commands.
Solution Approach 2:
The memory device performs preliminary monitoring of command patterns after activation to determine if precharging is needed. By watching for the absence of read/write commands within a threshold time window, the system prepares to precharge proactively, reducing latency compared to waiting for explicit precharge commands or correcting incorrect speculative predictions.
2Speed
If read-only activations keep pages open for extended periods to maintain fast access, then access latency is reduced, but power consumption increases
Solution Approach 1:
The system uses periodic monitoring of command patterns to determine when to close row buffers. Instead of keeping row buffers open continuously, the memory device periodically checks whether new read/write commands are issued to the same row and closes (precharges) the row buffer when no activity is detected within a threshold period, creating a dynamic on/off pattern that reduces power consumption while maintaining performance.
Solution Approach 2:
The row buffer management transitions from static (always open or always closed) to dynamic behavior. The memory device adapts row buffer state based on real-time command patterns, keeping row buffers open only when necessary for performance and closing them when idle to save power, making the system flexible and responsive to actual workload conditions.
3Ease of operation
If traditional activate and precharge commands are used separately, then precise control over memory operations is achieved, but command traffic and complexity increase
Solution Approach 1:
The system merges the activate command with automatic precharge functionality. The activate command is enhanced to include monitoring and automatic precharge behavior, combining what were previously separate operations (activate followed by conditional precharge) into a single integrated command sequence that reduces command traffic while maintaining precise control.
Solution Approach 2:
The activate command is given multi-functionality by embedding automatic precharge logic within it. Instead of being a simple activation command, it now also performs monitoring and conditional precharging, reducing the need for separate precharge commands and simplifying the overall command interface while maintaining control precision.
Data Source
AI summary
Methods, systems, and devices for memory accessing with auto-precharge are described. For example, a memory system may be configured to support an activate with auto-precharge command, which may be associated with a memory device opening a page of memory cells, latching respective logic states stored by the memory cells at a row buffer, writing logic states back to the page of memory cells, and maintaining the latched logic states at the row buffer (e.g., while maintaining power to latches of the row buffer, after closing the page of memory cells, while the page of memory cells is closed).