Sandisk and SK hynix develop open HBF interface for AI systems
Sandisk and SK hynix have published the first technical specification for High Bandwidth Flash through the Open Compute Project. The companies began working on the standard in February, with Google and Tenstorrent later joining the HBF consortium.
HBF uses vertically stacked NAND flash to provide more capacity and bandwidth close to an AI accelerator. It targets inference workloads where large models require more memory than the HBM installed alongside GPUs and other processors can provide.
HBF is designed to work alongside HBM
The specification covers performance requirements, electrical guidelines and the interface between an HBF stack and its host processor. It also includes packaging and reliability guidance, along with software instructions for read and write operations.
© Sandisk Sandisk and SK hynix are not proposing HBF as a direct replacement for HBM. The specification allows both technologies to coexist in one system, with HBM handling workloads that require lower latency and HBF providing additional capacity for model weights and other inference data.
Sandisk previously said a 16-die HBF stack could provide 512GB of capacity while using a package similar in size to HBM. The company claimed HBF could offer eight to sixteen times more capacity than HBM at a similar cost. Its simulation using the Llama 3.1 405B model reportedly delivered performance within 2.2% of a system with unlimited HBM capacity.
First HBF samples targeted for 2026
Sandisk previously targeted the second half of 2026 for its first HBF samples. The first AI inference devices using the technology were expected to begin sampling in early 2027, although the latest announcement does not provide an updated product schedule.
The open specification gives accelerator, memory and system developers a shared interface before commercial HBF products become available. Sandisk, SK hynix and Google will discuss the technology during the Future of Memory and Storage Conference on August 6.
Sources: Sandisk PR
