Samsung, SK Hynix eye 2Q27 shipments of 8-layer HBM4 to Nvidia

The 8-layer specification matters more than the headline. Samsung and SK Hynix simultaneously locking into Nvidia's Rubin Ultra HBM4 supply is a dual-sourcing hedge against yield risk — Nvidia clearly hasn't forgotten Samsung's repeated HBM3E qualification slips in 2023. Technically, HBM4 introduces a logic base die into the stack for the first time. An 8-layer configuration is a compromise between TSV density and thermal management within manufacturable yield windows, not a bandwidth arms race. The real bottleneck isn't the DRAM die itself but the advanced-node foundry process for the base die — turning memory makers' dependency on TSMC's CoWoS capacity from optional to structural. On competition, Micron's share in Nvidia's HBM ecosystem is being further compressed. During the 2025–2026 qualification window, both Korean players will tilt capex toward HBM4 lines, disrupting traditional DRAM supply-demand equilibrium. A new memory pricing upcycle is likely in H2 2026. Over the next 12–24 months, Rubin Ultra's bandwidth demands will force HBM4E spec definition to advance to Q1 2026, while 8-layer HBM4 ramp-up overlaps with HBM4E design freeze. Korean memory makers face a capital squeeze: the previous generation hasn't hit full production, and the next is already locked in.