Broadcom has unveiled the Thor Ultra, an 800G Ethernet Network Interface Card (NIC) built specifically for large-scale AI workloads. It connects hundreds of thousands of XPUs and is designed around the Ultra Ethernet Consortium (UEC) specification, which aims to extend Ethernet into the world of high-performance AI networking.
AI clusters are getting huge, and with that comes a problem: the old interconnects can’t keep up. Proprietary fabrics like InfiniBand still dominate, but Broadcom’s new approach signals a move toward something more open. By adopting UEC, the company is making Ethernet a viable option for AI scale-out, giving system designers more freedom to choose hardware rather than being locked into closed ecosystems.
Reworking RDMA for Scale
One of the biggest challenges in AI networking is scaling RDMA across thousands of nodes. Standard RDMA lacks features like multipathing, selective retransmission, and congestion control that can adapt in real time. Thor Ultra adds all of these through a UEC-compliant RDMA engine, making it more capable in high-load environments where packet loss and congestion are inevitable.
It supports packet-level multipathing for better load balancing, out-of-order packet delivery directly to XPU memory, and both receiver- and sender-based congestion algorithms. In practice, that means higher fabric utilisation, faster job completion, and fewer stalls during large AI training runs.
Hardware and Design Features
Thor Ultra comes in standard PCIe CEM and OCP 3.0 form factors, using 200G and 100G PAM4 SerDes for long-reach copper. It connects to the host through a PCIe Gen6 x16 interface and includes line-rate encryption and decryption to reduce CPU load. Broadcom has also built in secure boot, signed firmware, and device attestation to protect against tampering.
It’s fully compatible with the company’s switching portfolio, Tomahawk 6, Tomahawk Ultra, and Jericho 4, creating a complete Ethernet ecosystem for AI-scale networking. For engineers building the next generation of data centres, this combination of 800G bandwidth and open architecture could make Ethernet a serious alternative to proprietary solutions.
To learn more, please visit www.broadcom.com
Image credit: Broadcom
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