---
title: A New Flash Memory Tier for AI Inference Now Has an Open Standard and a 512GB Ceiling
description: SK hynix and Sandisk published the first High Bandwidth Flash specification through the Open Compute Project, covering up to 512GB a stack.
author: Darie Nani (Editor-in-Chief)
date: 2026-08-04T09:54:55.766Z
updated: 2026-08-04T09:54:55.774Z
canonical: https://www.sovereignmagazine.com/article/hbf-open-standard-ai-inference-512gb
image: https://cdn.nanimediahouse.com/sk-hynix-nand-flash-hbf-97507.webp
categories: Science & Tech
content_type: News
region: Global
publication: Sovereign Magazine
schema_type: Article
---

An AI chip serving a trained model needs two things from its memory: the speed to move data quickly, and the room to keep enough of the model close to the processor. SK hynix says the memory structure the industry already has cannot deliver high capacity data processing and power efficiency at the same time once a model moves from training, which produces large language models, into inference, the stage where it serves users.

The layer the company has been developing with Sandisk to close that gap is High Bandwidth Flash, which sits between HBM and the SSD. SK hynix says it transfers data at speeds similar to HBM while leaning on NAND to expand capacity significantly. HBM continues to carry the high level of bandwidth, and HBF works as a supporting layer.

On 4 August, at the opening of FMS 2026 at the Santa Clara Convention Center in California, the two companies published the first standard specifications for HBF and disclosed them through the Open Compute Project. That comes about six months after they launched a consortium in February 2026, and follows the standardization partnership they announced in August 2025.

## The Specification Tops Out at 512GB a Stack

Capacity in the published specification reaches up to 512GB, across two stack configurations of 8-high and 16-high NAND dies. Bandwidth is sorted into three grades, Grade 1 to Grade 3, running from roughly 0.4TB/s to 3.0TB/s. The document also sets out connection interfaces and electrical characteristics, reliability and packaging guidelines for the HBF die stack process, and software input and output guidelines.

## The Link to the Processor Uses an Existing Chiplet Standard

For the connection between HBF and the processor, the specification adopts UCIe, or Universal Chiplet Interconnect Express, an industry standard interface. SK hynix says that choice lays the groundwork to integrate HBF flexibly across different processor types, including GPUs and CPUs.

## Google and Tenstorrent Have Joined the Consortium

SK hynix describes the Open Compute Project as the world's largest open data center technology initiative, and presents HBF as an open standard for the whole industry rather than proprietary technology. Google and Tenstorrent are taking part in the HBF consortium. The standardization work began at a kick-off event the two companies held at Sandisk's headquarters in Milpitas, California on 25 February, where they launched a dedicated workstream under OCP.

“The key to AI infrastructure is to go beyond the performance competition of individual technologies and to optimize the entire ecosystem,” Ahn Hyun, SK hynix president and chief development officer, said in February. The company expects HBF to lower total cost of ownership while making AI systems easier to scale, and points to industry forecasts that demand for complex memory solutions, HBF among them, will pick up around 2030.

“With the rapid spread of AI applications, we are at a point where overall data processing structures must be redesigned,” said Kim Chun-sung, SK hynix executive vice president and head of solution development, adding that through HBF the company will expand the boundaries between memory and storage and contribute to building new architectures that enhance overall system efficiency.

## The Capacity Claim Is 8 to 16 Times HBM, on Sandisk's Own Figures

Sandisk, whose CBA technology, CMOS directly bonded to array, underpins its work on HBF, has published the most specific numbers. In a fact sheet the company states that HBF can closely match HBM's bandwidth while delivering 8 to 16 times the capacity at a similar cost, and that it closely matches HBM4's physical footprint, power profile and stack height while offering 512GB of total capacity per 16-die stack. A further Sandisk figure, that HBF comes within a 2.2% delta of a hypothetically unlimited-capacity HBM when reading pretrained weights on a Llama 3.1 405B parameter model, is a simulated result rather than a measured one.

“NAND is one of the most scalable technologies out there,” said Alper Ilkbahar, Sandisk executive vice president, chief technology officer and a member of the HBF technical advisory board.

## The Technology Goes Back to a February 2025 Investor Event

Sandisk first showed HBF at an investor event in February 2025, after engineering groups across NAND design, ASIC design and packaging had spent close to two years developing it. Since then the company has taken an FMS Best of Show, Most Innovative Technology award for the technology, formed a technical advisory board, signed a memorandum of understanding with SK hynix, and set out a path for HBF products to reach customer sampling, targeted for 2026.

The specification lands alongside the rest of what SK hynix is showing at FMS 2026. Kim and Kang Uk-song, head of next generation product planning, give a joint keynote on 4 August titled “Orchestrating Efficient AI Infrastructure through Tiered Memory in the Era of Agentic AI.” On 6 August, SK hynix vice president Lim Eui-cheol joins Sandisk vice president Rajeev Nagabhirava and Google DeepMind senior staff engineer Xiaoyu Ma for a panel titled “Breaking the Memory Wall with High Bandwidth Flash.” The company is also showing its tenth generation 375-layer 4D NAND wafer and products publicly for the first time, which it says improve performance per watt by 2.5 times over the previous generation, with mass production of eSSDs based on them planned for early next year.

## FAQ

**Q: How does High Bandwidth Flash work?**
HBF is a memory layer that sits between HBM and the SSD. SK hynix says it transfers data at speeds similar to HBM while using NAND flash to expand capacity significantly. HBM continues to handle the high level of bandwidth a processor needs, and HBF acts as a supporting layer for capacity.

**Q: How much capacity and bandwidth does the specification cover?**
Up to 512GB, across two stack configurations of 8-high and 16-high NAND dies. Bandwidth is sorted into three grades, running from roughly 0.4TB/s to 3.0TB/s.

**Q: Is HBF an open standard or one company's technology?**
SK hynix and Sandisk developed it together and disclosed the specification through the Open Compute Project, which SK hynix describes as the world's largest open data center technology initiative. Google and Tenstorrent are taking part in the consortium alongside them.

**Q: When might HBF products reach customers?**
Sandisk has set out a path for HBF products to move into customer sampling, targeted for 2026. SK hynix points to industry forecasts that demand for complex memory solutions, including HBF, will pick up around 2030.