Samsung is leading in HBM4 certification, while SK Hynix and MU are addressing some minor issues and are also expected to obtain Rubin's certification.

Previously, SK Hynix was highly anticipated to lead in Rubin's HBM4 certification. However, performance issues forced SK Hynix to redesign its base chip. Consequently, NVIDIA scaled back this year's production ramp-up plan, and Samsung has taken the lead in Rubin's certification.

NVIDIA is likely to adopt Samsung's HBM4 chips for the launch and mass production of Rubin. MU has largely resolved its logic chip issues but is still addressing some performance problems with the base chip. The specific nature of these issues is unclear, but given that MU's HBM4 yield is understood to be below 30%, these problems appear to be related to low yield.

Ultimately, all three memory manufacturers are expected to be certified, as HBM4 capacity would be insufficient to support Rubin's launch without the participation of all three.