Memory Module Segmentation for Signal Integrity and Pin Count
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Solution Overview
Problem
Conventional memory modules face challenges in achieving stable signal integrity and high data transfer rates due to capacitive loading issues when operating at frequencies above 1 GHz, particularly with the increasing number of pins required for differential signaling, which exceeds mechanical design limits in current personal computer form factors.
Innovation Solution
The implementation of a memory system where a memory controller provides command/address signals to a specific memory device, which then repeats and distributes these signals to other devices within the module via internal buses, reducing capacitive loading and allowing for higher frequency operations without the need for excessive pin count, and merging the command/address bus with the write bus to minimize pin requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential signaling is used to achieve high data transfer rates above 3,200 Mbps, then signal integrity is improved, but the number of pins required doubles
Solution Approach 1:
The memory module divides memory devices into two groups: a first group directly coupled to the memory controller via point-to-point connections, and a second group coupled through memory devices in the first group. This segmentation allows differential signaling to be used selectively on critical paths while reducing the total pin count required at the memory controller interface.
Solution Approach 2:
Memory devices in the first group act as intermediaries, receiving command/address signals and data from the memory controller and forwarding them to memory devices in the second group. This intermediary approach enables high-speed differential signaling to be used internally within the memory module without requiring all memory devices to be directly connected to the controller with differential pairs.
2Quantity of substance
If conventional multi-drop command/address bus architecture is used, then pin count is reduced, but capacitive loading increases and signal integrity deteriorates at frequencies above 1 GHz
Solution Approach 1:
The patent replaces the conventional multi-drop command/address bus architecture with a point-to-point connection system. Instead of sharing a common bus that creates capacitive loading, each memory device in the first group has its own dedicated connection to the memory controller, eliminating the capacitive loading issue while maintaining reasonable pin counts through the hierarchical structure.
3Reliability
If point-to-point connections are used for all memory devices, then signal integrity is improved, but the number of pins exceeds mechanical design limits
Solution Approach 1:
The memory module segments memory devices into hierarchical groups where only the first group has point-to-point connections to the memory controller. The second group shares connections through the first group, creating a balanced architecture that provides point-to-point signal integrity where needed while reducing total pin count through shared internal connections.
Solution Approach 2:
The patent introduces a hierarchical dimension to the connection architecture, organizing memory devices in multiple levels or groups. This dimensional organization allows point-to-point connections at the first level for optimal signal integrity, while subsequent levels use shared connections to reduce the overall pin count, effectively distributing the connection burden across different hierarchical dimensions.
Data Source
AI summary
A memory module includes a port configured to receive write data and command/address signals and multiple memory devices. The multiple memory devices include a first set of the memory devices, each memory device of the first set coupled to the port, and a second set of the memory devices, each memory device of the second set configured to receive associated write data and associated command/address signals for the memory device through at least one of the other memory devices of the first set and the second set.