2-tier-gpu-fabric-calculator

2-Tier / 2-Plane Compute Fabric

GPU Compute Fabric BOM Calculator

2-Tier Backend Fabric · Nokia 7220 IXR-H5-64O · 8 GPUs/Server · 32 Servers/SU

NIC & GPU Configuration
Per-GPU NIC / Fabric Plane Mode
NIC Vendor (within mode)
GPU Platform
Cluster Size
Number of GPUs 1024 GPUs
256 (1 SU) 1024 2048 4096 8192 (32 SU)
Custom (any ×256)
Architecture Summary
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To alperen.akpinar@nokia.com
Subject [Nokia GPU Fabrics]
Bill of Materials
Component Role / Side Qty
Per-Plane Breakdown (Single Plane View)
GPU × NIC Compatibility Matrix (Nokia 7220 IXR-H5-64O fabric · Tomahawk 5 ASIC)
GPU Platform BCM Thor2 (400G, PCIe Gen5) NVIDIA CX7 (400G, PCIe Gen5) NVIDIA CX8 (800G, PCIe Gen6) BCM 800G (future / TBD)
Vendor-validated reference design Feasible · suboptimal (over- or under-provisioned) Future / not generally shipping
All combinations are SerDes-compatible with the H5-64O (Tomahawk 5): 800G OSFP cages run 4×200G PAM4 (CX8) or break out to 2×400G as 4×100G PAM4 (CX7 / Thor2). Compatibility is about reference validation, host PCIe generation, and bandwidth balance — not signaling.
Nokia 7220 IXR-H5-64O · 64 × 800G OSFP cages / 128 × 400GE logical ports · 64 server-facing + 64 spine-facing per leaf · 1:1 ratio
Spine count is rounded up to the next ECMP-friendly tier (power-of-2) so leaf-spine hashing distributes uniformly across all paths.
2-Tier (Leaf-Spine) · Max 8192 GPUs for this switch architecture (32 SU, 1 link/leaf-spine pair)
Created by Alperen Akpinar
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