Asymmetric Memory Channel Bandwidth Allocation
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Solution Overview
Problem
Existing modular memory systems face limitations in peak memory bandwidth due to noise from stub paths and increased costs with replicated memory channels, making it difficult to efficiently expand storage capacity while maintaining signaling rates.
Innovation Solution
The implementation of an expandable memory system with asymmetric memory channels, where memory channels of progressively reduced widths are dedicated to respective sockets, allowing for point-to-point signaling and re-allocation of signaling bandwidth as memory modules are added, thereby maintaining a fixed net signaling bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If separate, replicated memory channels are coupled point-to-point between the controller and respective memory-module sockets, then signaling rates and peak memory bandwidth are improved, but the number of controller interface pins and external signal lines increases, driving up cost
Solution Approach 1:
A single memory channel is designed to serve multiple memory module sockets through dynamic configuration. The channel can be allocated to different sockets based on system needs, allowing one physical channel to perform the function of multiple channels. This multi-functional approach maintains high signaling rates while reducing the total number of controller interface pins required.
Solution Approach 2:
The memory channel allocation is made dynamic rather than static. The system can reconfigure which socket receives the memory channel at different times, allowing flexible adaptation to various memory expansion scenarios. This dynamic allocation enables the same physical infrastructure to support different configurations without requiring additional pins for each potential socket.
2Productivity
If separate, replicated memory channels are coupled point-to-point between the controller and respective memory-module sockets, then peak memory bandwidth is improved, but cost increases
Solution Approach 1:
One memory channel is designed to serve multiple sockets through dynamic allocation, replacing the need for multiple dedicated channels. This universal channel can be configured to work with any installed memory module, providing high bandwidth performance while significantly reducing the cost of controller interface pins and external signal lines.
3Device complexity
If modular memory systems use shared memory channel with stub paths, then device complexity is reduced, but noise and signal reflections increase, limiting signaling rates
Solution Approach 1:
The problematic stub path segments are removed from the signal path. Instead of having signals traverse through unused sockets (creating stub paths), the system establishes direct point-to-point connections between the controller and installed memory modules. This extraction of harmful stub paths eliminates signal reflections and noise while maintaining a relatively simple overall system structure.
Solution Approach 2:
The memory channel structure is adapted locally based on which sockets are populated. When a socket contains a memory module, the channel is configured to provide a direct connection. When a socket is empty, the channel is allocated to a different populated socket. This local adaptation ensures optimal signal quality for each configuration without requiring a completely different overall architecture.
Data Source
AI summary
An expandable memory system that enables a fixed signaling bandwidth to be configurably re-allocated among dedicated memory channels. Memory channels having progressively reduced widths are dedicated to respective memory sockets, thus enabling point-to-point signaling with respect to each memory socket without signal-compromising traversal of unloaded sockets or costly replication of a full-width memory channel for each socket.