Memory Interface Status Signal Mechanism for Variable Latency
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Solution Overview
Problem
Traditional memory systems struggle with handling memory devices that require variable latencies, as they are constrained by fixed pre-determined latency values, leading to performance issues when devices need more time to respond to commands, and implementing feedback signals to stall controllers impacts unrelated commands.
Innovation Solution
A status signal mechanism that informs the host memory controller when a command may require more time, allowing the return of a status word on the data bus with reasons for the delay and recommended retry times, enabling dynamic latency management and autonomous data transfers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed pre-determined latency values are used in memory systems, then the system operates with predictable timing, but performance deteriorates when memory devices need more time to respond to commands
Solution Approach 1:
The patent implements dynamic latency adjustment by allowing memory operations to complete at variable latencies based on actual device readiness. The system transitions from fixed pre-determined latency to flexible timing where commands can be executed when memory devices are ready, improving throughput without sacrificing timing reliability through status signal mechanisms.
Solution Approach 2:
The patent employs feedback signals (such as DECODER_READY, DQ_READY, and other status signals) that provide real-time information about memory device readiness to the controller. This feedback mechanism enables the controller to adjust command timing dynamically, allowing operations to proceed when devices are ready rather than adhering to rigid fixed latency schedules.
2Reliability
If feedback signals are implemented to stall controllers when memory devices need more time, then timing constraints are satisfied, but unrelated commands are impacted and overall system performance decreases
Solution Approach 1:
The patent segments the memory system into independent command pipelines where individual commands can be stalled or accelerated without affecting others. Status signals are generated per-command rather than system-wide, allowing the controller to manage timing constraints for specific operations while maintaining throughput of unrelated commands through parallel processing and independent command queues.
Solution Approach 2:
The system dynamically adjusts command execution timing on a per-command basis rather than stalling the entire controller. The controller can selectively wait for status signals from specific memory operations while continuing to process other commands, creating a dynamic scheduling system that maintains high overall throughput while satisfying timing constraints for individual operations.
3Extent of automation
If status signal mechanisms are implemented to communicate latency needs, then autonomous data transfers are enabled, but device complexity increases
Solution Approach 1:
The patent implements status signal mechanisms that serve multiple functions: indicating command completion, signaling data readiness, communicating latency status, and enabling autonomous transfers. By making these status signals multi-functional, the system achieves high automation capability without proportionally increasing complexity, as the same signal infrastructure supports multiple operational modes and communication needs.
Solution Approach 2:
The patent combines status signal generation with existing memory interface logic, merging the latency communication function into the standard command execution pathway. Rather than adding separate dedicated latency signaling infrastructure, the system integrates status signal generation into the memory controller and device existing logic, reducing overall complexity while enabling autonomous data transfers.
Data Source
AI summary
In an example, the present invention provides a memory interface device. The device has a command interface, address interface, and a control interface device coupled, respectively, to a command address bus, an address bus, and a control interface bus of a host memory controller. The device has a status signal interface configured to output a status signal coupled to the data interface bus of the host memory controller. In an example, the status signal is asserted in an absence of data asserted on the data interface bus.