NVIDIA cuts Vera Rubin NVL72 NVLink bandwidth to 3.0 TB/s per Rubin GPU

NVIDIA has revised the Vera Rubin NVL72's NVLink bandwidth from 3.6 TB/s to 3.0 TB/s per Rubin GPU package, a reduction of about 17%, according to a post by SemiAnalysis on X. The post attributes the change to signal integrity problems in the design's bidirectional SerDes, which has a theoretical full-rate bandwidth of 448 Gbps per physical connection. It says crosstalk, insertion loss, and return loss create these challenges at that speed.

The report comes from a single source, and NVIDIA has not been quoted on the change or its cause in the reporting available here.