Nvidia’s Rubin Ultra GPU is moving forward with HBM4E memory, not the HBM4 used in its predecessor, and it is bringing a meaningful capacity upgrade along for the ride. The chip is targeting up to 768GB of HBM4E using 12-Hi stacks, a substantial leap from the 288GB of HBM4 that the current Rubin GPUs support.
The Kyber rack-scale platform, which includes the NVL144 and NVL576 systems, remains active and on schedule alongside Rubin Ultra for a second-half 2027 release.
What changed, and why it matters
The original Rubin Ultra design called for 1TB of memory using 16-Hi HBM4E stacks. That target has since been revised downward to 768GB via 12-Hi stacks, a direct response to anticipated supply constraints across the HBM4E production chain.
The company sources HBM from SK Hynix, Samsung, and Micron, and production of next-generation HBM4E is expected to be tight. Nvidia is also evaluating lower-capacity 8-Hi HBM4E configurations as a fallback, giving itself room to maneuver if procurement gets difficult.
