HBM4
Fourth generation HBM — JEDEC spec 2024, first product deliveries 2026. Double interface width (2048-bit vs HBM3's 1024-bit) ⇒ 2 TB/s+ per stack.
16-Hi stacks (16 dies high) become more common → 64 GB per stack possible. SK Hynix won the first H200/B100 design with hybrid bonding tech. Competitors: Samsung struggles to catch up after poor HBM3 yield, Micron is third. HBM supply is the biggest bottleneck for AI training in 2024-2025.