NVMe SSD
▶ See it in 3D The Memory Stack region
Flash storage — vast and cheap, but thousands of times slower than memory. It holds models and data at rest, never the live work. Runs on its own boom-bust cycle, separate from HBM.
What it is
PCIe Gen5 flash — ~14 GB/s but microsecond latency, 3–5 orders slower than DRAM. Holds weights at rest, checkpoints, last-ditch KV overflow.
The business
NAND oligopoly: Samsung, SK Hynix (Solidigm), Micron, Kioxia, plus controllers. AI lifts enterprise SSD demand but it is a separate cycle from HBM.
Bottleneck severity
Who makes it
Samsung005930.KS
#2 in HBM. Began HBM4 mass production in Feb 2026 and is qualified at NVIDIA — with an in-house 4nm base die, the one turnkey memory+logic+packaging offer. P5 Pyeongtaek pulled forward to late 2027; ~$73B cumulative capex through 2026.
SK Hynix000660.KS
#1 HBM maker (~62% share). Qualified HBM4 at NVIDIA first and holds an estimated 60–70% of Rubin's HBM4 allocation, with a TSMC-made logic base die. Sold out through 2027; its CEO calls 2027 potentially the tightest supply year the industry has seen. The bellwether of the whole cycle.
MicronMU
#3 HBM, the only US-HQ DRAM maker. Qualified on Rubin HBM4; sold out through 2027 and meeting only ~50–65% of what customers ask for. New Idaho capacity doesn't land until 2027–28 — so the squeeze is structural, not seasonal.
Metrics that move this layer
- NAND ASPflash cycle
- enterprise SSD bit-growthAI checkpoint/storage demand