BCOM Buffer Protocol for Dual Pseudo-Channel Memory Modules
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Solution Overview
Problem
Traditional BCOM commands lack sufficient bits to indicate all possible operating modes for two separate pseudo channels in LRDIMMs, forcing prior implementations to sacrifice burst on the fly operation, use of two ranks per pseudo channel, or non-target ODT, which limits cross-compatibility and increases complexity and cost.
Innovation Solution
A new BCOM command protocol is introduced that separates commands for Read/Write transactions to serve both pseudo channels, allowing the same number of signal lines and bits by inferring certain information, enabling support for burst on the fly and multiple ranks per pseudo-channel, and allowing non-target ODT control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional BCOM commands are used with fixed timing, then command structure remains simple, but insufficient bits to indicate all operating modes for two pseudo channels
Solution Approach 1:
The patent applies dynamics by making the BCOM command structure adaptive rather than fixed. The command format changes based on timing conditions - when pseudo channels are time-multiplexed, a first command format is used; when burst on the fly is needed, a second command format is used. This dynamic adaptation allows the same physical bus to carry different levels of information without changing hardware, resolving the contradiction between information capacity and structural complexity.
Solution Approach 2:
The patent changes the parameter of command bit allocation based on operational mode. By detecting timing conditions, the system dynamically adjusts which command format is transmitted, effectively changing the information capacity parameter without adding physical bits. This allows full indication of operating modes while maintaining the original BCOM bus structure.
2Adaptability or versatility
If more bits are added to BCOM commands to support two pseudo channels, then all operating modes can be indicated, but cross-compatibility of system designs is limited and complexity increases
Solution Approach 1:
The patent makes the BCOM command structure universal by designing it to handle multiple operating modes through timing-based differentiation rather than additional bits. The same physical command structure serves both traditional single-channel mode and two-pseudo-channel modes, maintaining cross-compatibility while enabling enhanced functionality through temporal separation and conditional format selection.
Solution Approach 2:
The command structure dynamically adapts its information density based on operational needs. When time-multiplexing is used, the command format is simplified; when burst on the fly is required, the format expands to include additional timing offset information. This dynamic behavior allows full versatility without permanently increasing structural complexity.
3Productivity
If burst on the fly operation is sacrificed to support two pseudo channels, then BCOM command structure remains simple, but data throughput is reduced
Solution Approach 1:
The patent enables burst on the fly operation by dynamically switching command formats based on timing conditions. When the timing conditions allow simultaneous access to both pseudo channels, the system uses the enhanced command format to enable burst on the fly, thereby increasing data throughput without permanently increasing protocol complexity.
Solution Approach 2:
The system changes the operational parameter of command format selection based on timing availability. By detecting whether time-multiplexed or simultaneous access is possible, the system dynamically adjusts the command structure to enable burst on the fly when beneficial, maximizing throughput without requiring permanent structural changes.
4Quantity of substance
If two ranks per pseudo channel are used, then data buffer capacity increases, but BCOM bus cannot provide sufficient information to manage channels
Solution Approach 1:
The patent dynamically adjusts the information provided in BCOM commands based on the operational mode. When two ranks per pseudo channel are configured, the system uses timing conditions to determine whether additional information is needed in the command format, allowing flexible management of increased buffer capacity without fixed structural changes.
Solution Approach 2:
The command information parameter is changed based on configuration. The system detects the operational mode and adjusts the command format accordingly, providing sufficient channel management information for two ranks per pseudo channel when needed, while maintaining simpler commands when fewer resources are active.
Data Source
AI summary
A memory module has data buffers coupled to a registered clock driver (RCD) via buffer communication (BCOM) bus. The memory module includes memory devices managed as a first pseudo channel and a second pseudo channel. The data buffers manage data transmission between the memory devices and a host based on commands received over the BCOM bus. The RCD can send a first BCOM command on the BCOM bus to the data buffer, the first BCOM command to specify a rank and a burst length for the first pseudo channel. The RCD can send a second BCOM command on the BCOM bus to the data buffer, the second BCOM command to specify a rank and a burst length for the second pseudo channel, and a timing offset relative to the first BCOM command.