CDNA4 Infinity Fabric 20% faster links (38.4 Gbps, 76.8 GB/s per direction)

CDNA4 increases Infinity Fabric link speed by 20%: from 128 GB/s per direction (CDNA3) to 153.6 GB/s per direction (CDNA4). The links are 16 bits wide and fully bidirectional, running at 38.4 Gbps. Per-link bidirectional bandwidth: 153.6 GB/s (76.8 GB/s each direction). Total aggregate P2P: 1075.2 GB/s (up from 896 GB/s on CDNA3). Total peak aggregate theoretical transport rate: 1203.2 GB/s (up from 1024 GB/s). The 7-link full mesh topology is unchanged. This 20% improvement directly translates to 20% higher AllReduce bandwidth for tensor parallelism. The CDNA4 whitepaper states: 'The Infinity Fabric links in the AMD CDNA 4 architecture run up to 20% faster generationally at 38.4Gbps for a total link bandwidth of 76.8GB/s IN EACH DIRECTION' and endnote MI350-007: 'up to 153.6 GB/s peak total aggregate theoretical transport data GPU peer-to-peer (P2P) bandwidth per AMD Infinity Fabric link'. DANGLING REF, LEFT UNRESOLVED (2026-10-04 cross-reference repair): affected_by_hardware also carries 'gfx950', an AMD GPU ARCHITECTURE CODE, not a record id, and it spans more than one accelerator record: amd-instinct-mi350x, amd-instinct-mi355x and amd-instinct-mi350p are all CDNA4 (gfx950). Because one value in this field resolves to several accelerator records, it cannot be rewritten to a single id, and the field is typed as accelerator ids so this is a mixed-bucket value that belongs in a sibling field for architecture codenames. Left unchanged deliberately.