Sandisk and SK hynix Release First HBF Spec: 512GB Capacity, 3 TB/s Bandwidth for AI Inference

12 Sources

Share

Sandisk and SK hynix released the first High Bandwidth Flash technical specification through the Open Compute Project, defining a new memory tier for AI inference systems. The specification establishes capacities up to 512GB with bandwidth ranging from 0.4 TB/s to 3 TB/s, using UCIe interconnect to bridge the gap between HBM performance and NAND capacity.

Sandisk and SK hynix Formalize High Bandwidth Flash Standard

Sandisk and SK hynix formally introduced the High Bandwidth Flash specification through the Open Compute Project, marking a significant milestone just six months after the consortium began work in February 2025

1

5

. This new memory technology promises to address unprecedented memory demands in AI inference systems by combining the non-volatility of NAND flash with performance approaching High Bandwidth Memory. The specification was released as an open standard rather than a proprietary interface, giving AI data centers and system designers a common technical framework for incorporating HBF technology where larger, near-compute memory capacity and higher bandwidth are needed

2

.

Source: Korea Times

Source: Korea Times

Google and Tenstorrent joined as consortium members during the standardization process, contributing to technology validation and establishment of the standard

5

. Sandisk CTO Alper Ilkbahar explained that HBF was conceived to meet the unprecedented memory demands of AI inference workloads and accelerators, providing system builders with a practical path to placing high-capacity memory and compute units closer together

2

.

Technical Specifications Define Three Bandwidth Grades

The initial specification defines HBF packages with capacities up to 512GB using either 8-Hi or 16-Hi NAND stacks, though these are specialized devices with fast interfaces rather than standard 3D NAND stacks

1

. Performance is divided into three bandwidth grades ranging from approximately 0.4 TB/s to 3 TB/s, suggesting a multi-year roadmap with multiple implementations and generations

1

. The most capable implementation at 3 TB/s is positioned to beat the memory bandwidth of a single HBM4 memory stack at 2 TB/s, though it will likely trail in latency

1

.

HBF's pitch focuses on capacity rather than raw speed. A 512GB HBF stack provides eight to ten times the capacity of an HBM4 stack, which typically holds 48GB to 64GB, while the top HBF grade's 3 TB/s bandwidth lands within the 2.0 to 3.3 TB/s band typical of HBM4

3

. The specification establishes electrical and interface characteristics, packaging and reliability guidelines for stacked HBF devices, as well as software I/O requirements for read and write operations

1

2

.

UCIe Integration Enables Heterogeneous Computing Platforms

SK hynix claims that HBF uses the Universal Chiplet Interconnect Express standard to simplify integration with heterogeneous computing platforms, while Sandisk references the xPU-HBF interface, which could be its definition of UCIe implemented by companies like Broadcom or Marvell

1

. This adoption of UCIe as the link between an HBF stack and a host processor enables the technology to attach to GPUs and CPUs from different vendors

3

.

Source: Tom's Hardware

Source: Tom's Hardware

Extracting 400 GB/s of bandwidth from a single 512GB HBF package requires sophisticated engineering. Sandisk planned to use 16 HBF core dies featuring many arrays that can be accessed concurrently using dedicated read/write paths

1

. Reaching over 400 GB/s of bandwidth per package is possible using a single UCIe interface running at up to 64 GT/s with 64 lanes, though this means the HBF base die will be a fairly complex piece of silicon

1

.

HBF Addresses AI Model Weights While HBM Handles KV Cache

HBF leverages parallelism to overcome NAND's inherent speed limitations. While NAND offers roughly 1,000x slower read speeds than DRAM-based HBM, the logic die schedules thousands of parallel reads of NAND cells simultaneously, delivering cumulative bandwidth of 0.3 TB/s to 3 TB/s versus just around 6.4 GB/s for a JEDEC-spec HBM4

4

. This creates a practical division of labor: HBF stores AI model weights that require high read bandwidth but infrequent writes, while HBM continues handling KV cache that demands frequent writes

4

.

An AI model with 100 billion parameters operating at fp16 compute level requires 200GB just for storing model weights, which can quickly exhaust available HBM capacity

4

. By shifting model weights to HBF, systems can free up HBM for KV cache, enabling longer model context without compromising output accuracy. This bifurcation addresses the memory bottleneck that currently forces expensive GPU count increases to expand HBM capacity

4

.

Source: Wccftech

Source: Wccftech

Timeline and Industry Adoption Questions Remain

Sandisk has been working to a public roadmap since August 2025, targeting first samples of the memory itself in the second half of 2026 and samples of the first AI inference devices built with HBF in early 2027

3

. Industry expectations place actual commercialization between late 2027 and 2028, with volume data center demand justifying the investment arriving closer to 2030

3

.

The biggest question about HBF remains industry adoption. Since Sandisk and SK hynix announced collaboration plans in 2025, only Google and Tenstorrent have expressed interest in participating in the HBF consortium

1

. Notably absent are AMD, Broadcom, Intel, Nvidia, Marvell, Micron, Qualcomm, Samsung, and Western Digital, raising questions about ecosystem support despite the open standard approach through the Open Compute Project

1

. Watch whether major AI accelerator manufacturers and hyperscalers commit to HBF integration, as their participation will determine whether this new memory technology becomes a de facto standard for AI workloads or remains a niche solution.

Today's Top Stories

© 2026 TheOutpost.AI All rights reserved