Memory Controller With Speculative Precursor Commands for LPDDR5 Timing
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Solution Overview
Problem
Existing memory controllers face challenges in optimizing data throughput by efficiently scheduling memory access requests while adhering to the timing constraints of memory devices, particularly in protocols like LPDDR5 and LPDDR5X, where the scheduling of precursor commands such as ACTIVATE procedures limits the flexibility and efficiency of data bus utilization.
Innovation Solution
The implementation of speculative precursor commands, specifically allowing the early issuance of ACT1 commands relative to the ACT2 commands, provides increased flexibility to the command scheduler by enabling the ACT1 command to be sent earlier than traditionally allowed, thereby optimizing the selection of higher priority commands like read or write operations within the timing constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional memory access protocols are used with strict timing constraints, then timing compliance is ensured, but data throughput is limited
Solution Approach 1:
The patent applies preliminary action by allowing the ACT1 precursor command to be issued before the ACT2 precursor command, rather than waiting for ACT2 to be ready. This reordering enables the memory controller to start the activation process earlier, improving data throughput while still meeting timing constraints through speculative execution and validation mechanisms.
2Adaptability or versatility
If precursor commands are strictly scheduled according to protocol specifications, then protocol compliance is maintained, but command scheduler flexibility is reduced
Solution Approach 1:
The patent applies dynamics by making the command scheduling flexible and adaptive rather than rigid. The controller dynamically adjusts the issuance timing of ACT1 and ACT2 commands based on system conditions, using speculative execution where ACT1 is issued early and then validated. This dynamic approach increases scheduler flexibility while maintaining protocol compliance through validation mechanisms.
3Productivity
If ACT1 command is issued early to optimize throughput, then data bus utilization improves, but timing constraint violation risk increases
Solution Approach 1:
The patent applies preliminary action by issuing the ACT1 command before the traditional timing window would allow, effectively performing the activation preparation early. This early issuance improves data bus utilization by keeping the bus busy with useful work. The speculative nature of this early issuance is managed through validation to ensure timing constraints are ultimately met.
Data Source
AI summary
A memory controller includes a command scheduler, a timer and an interface configured to transmit memory access commands, including primary and secondary precursor memory access commands, to a memory. The command scheduler selects memory access commands associated with memory access requests. The timer indicates expiration of first and second time periods. The first time period is shorter than the second time period by a designated amount and the second time period is greater than or equal to a minimum time between a prior memory access command and a secondary precursor memory access command for the memory. The command scheduler allows selection of a primary precursor memory access command when the first time period has expired and allows selection of a secondary precursor memory access command when the second time period has expired.