Optimizing AI Infrastructure: The Advantages of OCP Busbar Power For GPU Modules And Full Rack

Author: Vincent Chen, System Architect, Pegatron Collection: 2025 OCP Global Summit - Expo Hall Sessions

Summary

Pegatron presents a high-density GPU rack design using the OCP ORv3 busbar architecture to maximize GPU density within a 51OU rack. The design packs 128 AMD Instinct MI355X GPUs and 32 AMD EPYC 9005 processors into a single rack using a 1,900 amp ORv3 power busbar. The system uses eight 33 kW power shelves delivering a total rack power of 162.4 kW (corrected from transcript's 126 kW based on slide data), with the complete rack weighing 1,691 kg (3,728 lbs) and measuring 600 x 2616 x 1265 mm (23.62 x 103 x 49.8 inches).

The server design uses a 5U form factor (2U+1U+2U) with 16 MI355X GPUs per server arranged in an 8-way baseboard configuration. Each server contains two GPU chassis (8x MI355X each) in the top and bottom 2U sections, with four AMD EPYC 9005 CPUs in the middle 1U section. The PCIe topology uses two CPUs with four PCIe switches, where each switch connects to two GPUs and one NIC (CX7/Thor2 400G), resulting in two GPUs sharing one NIC. The CPUs are interconnected via three xGMI links for high-bandwidth inter-CPU communication. The server weighs 108 kg and uses liquid cooling with a cold plate design developed in partnership with cooling vendors.