Nvidia reportedly weighing reduction of HBM capacity in Rubin Ultra chips due to persistent memory shortage, indicating production plan constraints from supply bottleneck.

NVIDIA is reportedly considering a significant reduction in the HBM capacity of its upcoming Rubin Ultra GPU, falling far short of what Jensen Huang announced at last year's developer conference. When Huang introduced Rubin Ultra, he highlighted 1TB of HBM4E memory spread across 16 stacks per GPU. However, sources familiar with testing indicate that NVIDIA has run at least three different Rubin Ultra variants in recent weeks, with some samples featuring dramatically reduced memory ranging from 192GB to 256GB. A few configurations have even reverted to HBM4 instead of the newer HBM4E specification and employ fewer memory stacks than originally planned.

The underlying cause is a production bottleneck: memory makers are unable to manufacture HBM4E fast enough to meet Rubin Ultra's original timeline. NVIDIA is therefore exploring lower specifications to maintain its production schedule. This mirrors similar memory adjustments across the industry, including reduced RDIMM capacities and cutbacks to SOCAMM modules on NVIDIA's Vera Rubin Superchip.

For a company of NVIDIA's scale to redesign its flagship chip around memory availability underscores the severity of the memory shortage and gives SK Hynix and Samsung considerable leverage. Industry observers expect elevated HBM pricing to persist.

Samsung Electronics has meanwhile locked in its DRAM roadmap for next-generation HBM products. The company plans to deploy 10nm-class 6th-generation (1c) DRAM as the core die for both HBM4 and HBM4E. For HBM5E—the 9th-generation HBM standard—Samsung intends to transition to 10nm-class 7th-generation (1d) DRAM. This staggered node transition allows Samsung to mature 1d yields before committing the next major HBM generation to the new process while retaining 1c as a reliable fallback option.

Samsung Electronics initiated main construction on its P5 Phase 1 facility last month and has begun deploying cleanroom equipment in earnest. In July, the company signed a cleanroom product supply contract with Shinsung E&G valued at 15.6 billion KRW, running through February 20, 2026.