AMD Unveils Instinct MI455X: CDNA 5 and Helios Take Aim at Nvidia
AMD's CDNA 5-based Instinct MI455X and 72-GPU Helios rack-scale system offer a serious new challenge to Nvidia's Rubin platform in AI data centers.
At its Advancing AI event, AMD detailed the Instinct MI455X accelerator built on its new CDNA 5 architecture, paired with the Helios rack-scale system that links 72 GPUs into a single coherent domain. AMD positions this as its most advanced AI chip yet and its first true rival to Nvidia's NVL72 rack design.
The MI455X packs 320 billion transistors using a hybrid chiplet approach that combines TSMC's 2N GAA process for compute dies with N3P for fabric and I/O dies, joined via CoWoS-L packaging. CDNA 5 renames the core compute unit a 'Work Group Processor' and shrinks wavefront width from 64 to 32 threads, cutting instruction latency and improving flexibility for tensor workloads. Low-precision MXFP4/MXFP8 throughput can reach up to 4x that of the previous generation.
Memory is a standout advantage: each MI455X offers 432GB of HBM4 at 23.3 TB/s, outpacing Nvidia's first Rubin GPU at 288GB and 22 TB/s. At rack scale, 72 GPUs deliver 31.1TB of aggregate HBM capacity — roughly 50% more than Vera Rubin's 20.7TB.
AMD cautions that real-world performance will likely trail these peak FLOPS figures, with software optimization remaining the key challenge. Still, newly announced deals with Microsoft and Anthropic signal tangible momentum in AMD's push for data center share.