AMD Unveils MI455X AI Accelerator and Helios Rack-Scale Architecture to Compete with Nvidia
At its Advancing AI 2026 event, AMD revealed the Instinct MI455X GPU, a 320-billion-transistor chip built on TSMC's 2N GAA process with CDNA 5 architecture. The accelerator features four Accelerator Complex Dies (XCDs) stacked on Fabric and Cache Dies using hybrid bonding, connected to 12 HBM4 memory stacks via CoWoS-L packaging. AMD also introduced the Helios rack-scale architecture, linking 72 MI455X GPUs into a coherent system to rival Nvidia's NVL72 design. The MI455X offers theoretical peak performance of 40.26 PF in OCP MXFP4 format, surpassing Nvidia's Rubin in some metrics. Key architectural changes include a shift to 32-wide wavefronts and enhanced transcendental math units. AMD announced customer wins with Microsoft and Anthropic, though cautioned that real-world performance may be lower than theoretical peaks.
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