CONCEPT Cited by 1 source

400 VDC rack power

Definition

400 VDC rack power is a data-center power-distribution scheme in which the rack is fed by a 400 V DC bus (as opposed to the more conventional 48 VDC bus-bar used in OCP v1/v2 racks, or the legacy 208–480 VAC PDU input). Higher voltage reduces the current required for a given power level, which reduces copper cross-section and I²R losses.

Meta × Microsoft's 2024 instance — Mount Diablo

"Our current collaboration focuses on Mount Diablo, a new disaggregated power rack. It's a cutting-edge solution featuring a scalable 400 VDC unit that enhances efficiency and scalability. This innovative design allows more AI accelerators per IT rack, significantly advancing AI infrastructure." (Source: sources/2024-10-15-meta-metas-open-ai-hardware-vision)

Mount Diablo is a disaggregated power rack (separate from the IT rack) with a scalable 400 VDC unit. By moving the power conversion out of the IT rack and into its own dedicated rack, two wins are claimed:

1. More usable U-space in the IT rack for compute, switching, and cooling manifold hardware.
2. Higher efficiency at 400 VDC than traditional 48 VDC for the ≥ 100 kW regime.

Why it matters

• Current scales inversely with voltage. At 100 kW rack power: 48 VDC ≈ 2 kA current; 400 VDC ≈ 250 A. The reduction in current reduces copper volume, connector mass, and resistive loss by order ~8×.
• Enabling technology for ORv3 HPR at 140 kW. ORv3 HPR racks that support Catalina at 140 kW are physically more feasible when the power-rack side is 400 VDC.
• Industry alignment precondition. Moving to 400 VDC requires standardizing connector families, protection schemes, and power-shelf architectures — exactly the kind of cross-industry coordination OCP provides.

Seen in

• sources/2024-10-15-meta-metas-open-ai-hardware-vision — Meta × Microsoft Mount Diablo announcement.

Related

• concepts/rack-level-power-density — the binding constraint higher voltage DC helps relax.
• concepts/liquid-cooled-ai-rack — thermal-side counterpart: liquid cooling + 400 VDC together unlock the 140 kW envelope.
• systems/mount-diablo-power-rack — the canonical wiki instance.
• systems/orv3-rack — the ORv3 HPR chassis that consumes Mount Diablo power.
• systems/catalina-rack — the AI rack at the consuming end.
• patterns/pdu-doubling-for-power-headroom — the Dropbox instance of the opposite-end-of-the-power-spectrum response to the same underlying rack-power-density constraint.
• companies/meta.