AMD’s Helios rack uses 72 MI455X GPUs and 260 TB/s of scale-up bandwidth
SumitGup · x · 2026-07-25
AMD's Helios rack-scale platform ties 72 MI455X GPUs into one shared-memory system
The post breaks down AMD’s Helios rack-scale AI architecture, which uses 72 MI455X GPUs, 12 Broadcom Tomahawk 6 ASICs, and 36 parallel network planes to deliver 3.6 TB/s bidirectional bandwidth per GPU and 260 TB/s aggregate scale-up bandwidth.
- UALoE defines GPU-to-GPU communication semantics, including memory reads and writes, ordering, and traffic distribution across the 36 planes.
- ESUN provides the Ethernet fabric underneath, handling forwarding, flow control, congestion management, retries, and small-message transport.
- The result is a rack where 31 TB of HBM4 remains physically distributed but can be accessed as if the whole cabinet were a single tightly coupled computer.
The image also shows the scale-up architecture as an Ethernet-based stack built around UALoE, OCP SUE, and ESUN, with AMD, Broadcom, Cisco, Meta, Microsoft, NVIDIA, and others listed as founding members.
Related event: AMD Launches MI455X and Helios, Escalating AI Compute to Rack-Scale(9 posts)→
More from Infra
- Grid queues make power architecture an AI-factory decision; Exowatt and Redwood offer fixes — ingliguori · 2026-10-27
- Two CVSS 9.9 Wasmtime flaws allow sandbox escape, one ARM64-only since 2020 — basedjensen · 2026-10-27
- AI Infra Meme: While Countries Need TW-Scale Power for Datacenters, People Argue About Lightbulbs — mgostIH · 2026-10-27
- NVIDIA reportedly stops taking RTX 5090 orders from board partners, even backorders — chemist_slime · 2026-10-27
- Legora runs 2,000 parallel agent evals on Modal Sandboxes for legal AI — blelbach · 2026-10-27
- Cloud release velocity scores: AWS 95, Azure 90, Google Cloud 82 — DavidLinthicum · 2026-10-27