Wavelength-Routed Memory Interconnects for High Bandwidth, Low Latency
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Solution Overview
Problem
Conventional memory systems face challenges in achieving high bandwidth and low latency while managing irregular memory-access patterns, with contention issues arising from shared resources leading to increased latency and variability.
Innovation Solution
A low-latency memory (LLM) architecture utilizing silicon photonic interconnects with optical parallelism and wavelength routing, incorporating an arrayed waveguide grating router (AWGR) for dedicated data paths and fine-grained memory banks to reduce contention and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DRAM and HBM technologies are used to improve memory bandwidth, then bandwidth is improved, but latency and variability in memory-access time increase due to deeper queues in the memory controller
Solution Approach 1:
The patent segments the memory access path by introducing wavelength-division multiplexed optical interconnects that parallelize the data transmission path. Each wavelength channel operates independently, allowing simultaneous memory accesses without queuing contention, thereby reducing latency while maintaining high bandwidth.
Solution Approach 2:
The patent replaces the electrical signal-based memory interconnect with an optical interconnect system. This substitution eliminates the contention and queuing issues inherent in electrical buses by using wavelength-division multiplexing, where multiple data streams can traverse the same physical path simultaneously without interference.
2Loss of time
If resources (buffers, ports, data/command/control buses, DRAM cells) are increased to reduce contention, then latency is reduced, but the cost and physical limits (such as number of pins) increase
Solution Approach 1:
The patent makes the optical interconnect infrastructure universal by enabling any processing unit to access any memory bank through wavelength routing. The AWGR and tunable transceivers provide multi-functional connectivity, eliminating the need for dedicated dedicated physical paths for each memory access, thereby reducing the total number of pins and resources required.
Solution Approach 2:
The patent adds the wavelength dimension to the data transmission medium. Instead of increasing the number of physical data buses or pins to reduce contention, the system multiplexes multiple data streams onto a single optical bus by assigning different wavelengths, effectively adding a new dimension to the communication space.
3Loss of time
If wavelength routing with AWGR is used to provide dedicated data paths, then contention is reduced and latency is optimized, but device complexity increases due to optical components
Solution Approach 1:
The patent merges the optical transceiver functionality directly with the memory banks and processing units, integrating the optical interface into the existing hardware architecture. This consolidation reduces the number of separate optical components needed and simplifies the overall system while maintaining the wavelength routing benefits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The LLM architecture optimizes latency, bandwidth, and energy efficiency by providing contention-less optical data paths and fine-grained memory banks, reducing queuing and interconnect latency, and minimizing bank conflicts.
Implementation Method 1
an arrayed waveguide grating router (AWGR) for dedicated data paths and fine-grained memory banks to reduce contention and latency
Implementation Method 2
A respective processing unit is coupled to an array of tunable optical transceivers
Implementation Method 3
WDM-based optical interconnects
Data Source
AI summary
One embodiment provides a computer system. The computer system includes a plurality of processing units, a plurality of memory channels, and an arrayed waveguide grating router (AWGR). A respective processing unit is coupled to an array of tunable optical transceivers. A respective memory channel is coupled to a plurality of memory banks. Each memory bank is associated with a unique optical wavelength and can be accessed via the corresponding wavelength. Each memory channel is coupled to an individual output port of the AWGR, and the tunable optical transceivers of each processing unit are respectively coupled to different input ports of the AWGR, thereby allowing each processing unit to communicate with any memory bank associated with any memory channel using an appropriate tunable optical transceiver tuned to the corresponding optical wavelength associated with the memory bank.