# Scale-up fabric (GPU-to-GPU inside the rack/pod)

Part ID: 3.01 · Layer 3 (Networking & interconnect)

The fabric linking GPUs to each other inside a single rack or pod, separate from the switching fabric that connects racks to each other.

Scale-up fabric is the shortest, highest-bandwidth network in the data center: it lets GPUs inside the same rack or pod address each other's memory directly, rather than going through the scale-out switch fabric (3.02, 3.03). It sits upstream of the copper spine and backplane cartridges (3.10) that physically wire it together and, at higher speeds, of the optics and co-packaged approaches (3.04, 3.08) being evaluated as a copper replacement. AI training and inference workloads that split a single model across many accelerators depend on this fabric scaling in lockstep with GPU count, since it sets the ceiling on how large a tightly coupled GPU domain can get. An investor should watch whether a proprietary approach keeps its lead over open alternatives being pushed by a wider industry consortium, since that split determines how concentrated the supplier base for switch chips, cables, and connectors stays as pod sizes grow.

**AI delta:** Larger AI models split across more GPUs per training or inference job, which raises the bandwidth and reach demanded of the scale-up fabric linking them inside a rack or pod.

## Companies

| Company | Role | Confidence | Ownership | Ticker | Note |
|---|---|---|---|---|---|
| Alphabet (Google) | manufacturer | inferred | public | GOOGL | ICI |
| AMD | manufacturer | inferred | public | AMD | Infinity Fabric |
| Astera Labs | manufacturer | inferred | public | ALAB | Scorpio X |
| Broadcom | manufacturer | inferred | public | AVGO | scale-up Ethernet (Tomahawk Ultra) |
| Nvidia | manufacturer | inferred | public | NVDA | NVLink/NVSwitch |
| UALink consortium | manufacturer | inferred | cooperative |  | members: AMD, Broadcom, Astera, Marvell, Cisco, hyperscalers |

Confidence tags: disclosed = company/filing statement; reported = trade press or partner list; inferred = taxonomy lead.