How 800G Switches Connect to 400G NICs with NVIDIA SN5600 and 4x100G PSM4
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Introduction: Meeting the Needs of Scalable AI and HPC Networks
Modern data centers and AI infrastructure require flexible, high-bandwidth solutions to keep up with the explosive growth of workloads. A common architecture today involves leveraging 800G switches to interconnect with 400G NICs, optimizing port utilization and link efficiency.
This article explores how to effectively connect NVIDIA SN5600 800G InfiniBand switches with 400G NICs using 4x100G PSM4 transceivers and breakout modules such as the Q112-400G-SR4.
800G Switches: High-Density Networking with NVIDIA SN5600
The NVIDIA SN5600 is a next-generation 800G InfiniBand switch built for AI fabrics and large-scale HPC environments. It supports:
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800G OSFP ports with breakout capability
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Low latency and high throughput
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Compatibility with split 2x400G and 4x100G breakout topologies
When paired with high-performance optical modules, the SN5600 switch becomes the backbone of advanced data networks.
400G NICs: The Rise of Q112-400G-SR4
The Q112-400G-SR4 is a 400G SR4 optical transceiver operating over multimode fiber with MTP/MPO-12 connectors. It offers:
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400G transmission over OM4 fiber up to 100 meters
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Compatibility with breakout from 800G OSFP ports
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Interoperability with 4x100G PSM4 setups or direct 400G links
These modules are commonly used in NICs that operate in 2x200G or 4x100G configurations for flexible top-of-rack deployments.
Using 4x100G PSM4 for Breakout Architecture
To connect a single 800G OSFP port to multiple 400G NICs, many data centers use a 4x100G PSM4 breakout configuration, which:
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Divides one 800G port into four 100G lanes
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Enables cost-efficient interconnects over parallel single-mode fiber
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Maintains signal integrity for short- to mid-range connections (up to 500m or more)
This setup provides high-density, modular scaling with simplified cabling.
Topology Diagram (Simplified)
[ NVIDIA SN5600 (800G) ]
|
800G OSFP
|
4x100G Breakout
┌────────┬────────┬────────┬────────┐
[100G NIC][100G NIC][100G NIC][100G NIC]
This is often combined with Q112-400G-SR4 modules in NICs, which accept either full 400G links or breakout 100G links, depending on deployment needs.
Why Use 800G to 400G Interconnects?
1. Future-Proof Bandwidth
800G switches support current 400G NICs while paving the way for upcoming full 800G server deployments.
2. Cost Optimization
Avoid costly full 800G NIC upgrades by utilizing 400G breakouts.
3. Network Flexibility
Supports mixed-mode operation with 800G-to-400G and native 800G-to-800G links on the same switch.
Conclusion: Building Scalable 800G-to-400G Networks
By leveraging NVIDIA SN5600, Q112-400G-SR4, and 4x100G PSM4 breakout cables, data center architects can efficiently scale AI, HPC, and cloud infrastructures. This hybrid approach balances bandwidth, flexibility, and cost—while remaining compatible with future 800G deployments.