72-GPU Blackwell Ultra MRC Rack — Arista 7060XE7 + Nvidia HGX B300

9 × HGX B300 (72 B300 GPUs) · 8× CX-8 SuperNIC per node @ 800G · 8 MRC planes · 16× 7060XE7 · 57.6 Tbps aggregate

Reference architecture aligned with OCP MRC Rev 1.0 and the OpenAI MRC paper. ConnectX-8 SuperNIC is Nvidia's reference platform (paper Clusters A/B on GB200). This rack uses HGX B300 and Arista 7060XE7 — GPU and switch SKUs differ from the paper testbeds.