Samsung Electronics' sixth-generation HBM4 has reached the 80% yield threshold, a level chipmakers often view as the point where defect rates, output stability and profitability materially improve, sharpening a market contest with SK Hynix that is increasingly centered on manufacturing scale rather than pure process development. Samsung improved HBM4 yields from below 60% when mass production began in February to about 80% within roughly six months, and said third-quarter HBM4 revenue will expand more than threefold from the prior quarter while HBM4 accounts for more than 60% of total HBM revenue in the second half. The company is also pursuing a year-end goal of lifting HBM market share to around 38%, near its DRAM market share, as UBS forecast Samsung could take 41% of HBM bit shipments next year versus 39% for SK Hynix after SK Hynix leads this year at 48%. SK Hynix, however, said HBM4 competitiveness depends on stable mass production, yields and quality, and industry participants believe its HBM4 yield has also climbed into the 80% range. Samsung is expanding capacity at its Hwaseong and Pyeongtaek campuses and has shipped HBM4E 12-high samples to major customers, while saying HBM4E reliability test yields have exceeded 70%. Even so, supply remains tight enough that Nvidia and AMD are considering lower-spec memory configurations for next-generation AI accelerators, including Rubin Ultra and MI400, as companies adapt to limited availability of HBM4E 12-high stacks. Analysts say that supply crunch could preserve pricing power for South Korean memory suppliers into next year, even as some warn that slower adoption of the most advanced memory configurations may weigh on long-term technology momentum.