Specifications

Overview

High Bandwidth Flash (HBF) is a next-generation memory/storage architecture that combines the non-volatility and capacity of 3D NAND with the high bandwidth of HBM-class memory. On August 3–4, 2026, SK hynix and SanDisk released the first open HBF technical specification through the Open Compute Project (OCP) — the industry's first standard of its kind — defining the system interface, electrical characteristics, reliability and packaging guidelines for HBF die stacks, and a software I/O guide for read/write operations.

The specification targets AI inference systems where LLM weight capacity and bandwidth bottlenecks collide. It defines HBF packages up to 512GB using 8-Hi or 16-Hi NAND die stacks, scalable bandwidth across three grades from roughly 0.4 TB/s to 3.0 TB/s, a dedicated xPU–HBF host interface with UCIe support, and a 375-layer 4D NAND claimed to be 2.5× more power efficient than conventional stacks. The consortium began work in February 2026, following the initial SK hynix–SanDisk partnership formed in August 2025 — positioning HBF as an open, multi-vendor path to giving AI accelerators terabytes of near-memory capacity at a fraction of HBM's power budget.