HBM4
The next high-bandwidth-memory generation with wider interfaces and a logic base die, targeting late-2020s accelerators.
Current numbers
~2.9 EF FP4AMD Helios (72× MI455X) rack-scale FP4 (1.4 EF FP8), 31 TB HBM4, ORW double-wide
~288 GBHBM4 per Rubin GPU at ~22 TB/s; trajectory H100 80 GB → H200 141 GB → HGX B200 180 GB → B300 288 GB, flat into Rubin, then Rubin Ultra 1 TB
~$300 → ~$500–600+ per stackreported 12-Hi stack price, HBM3E → HBM4 (8–12 stacks per accelerator)