NVIDIA's original four-die version of the Rubin Ultra GPU, unveiled at GTC 2026 three months ago, has been cancelled due to manufacturing constraints TSMC cannot yet solve, semiconductor research firm SemiAnalysis confirmed on June 30. The GPU that will ship in 2027 under the Rubin Ultra name will deliver roughly half the compute and half the memory bandwidth of what was announced. The cancellation signals that TSMC's CoWoS-L advanced packaging technology has hit a physical ceiling at the four-die scale, and its successor CoPoS is not expected to enter mass production until late 2028 at the earliest. The four-die design would have required an interposer spanning roughly 7.5 to 8 times the reticle limit, and assembling more than 3,400 square millimeters of active silicon onto a single interposer introduces severe substrate warpage, creating electrical failures and dramatically suppressing manufacturing yield. NVIDIA has not publicly commented on the design change.