--- description: "High Bandwidth Flash gets its first OCP spec from Sandisk and SK hynix: 512GB stacks, 3.0TB/s grades, plus 60% denser BiCS10 QLC." title: "High Bandwidth Flash Gets Its First Open Spec: 512GB Stacks and Up to 3.0TB/s" image: https://www.storagereview.com/wp-content/uploads/2026/08/StorageReview-Sandisk-HBF-Memory-Tier-2.png --- [![Storage Review]()](https://storagereview.com/) --- [Facebook](https://www.facebook.com/@storagereview) [X (Twitter)](https://twitter.twitter.com/storagereview) [Instagram](https://www.instagram.com/storagereview/) [LinkedIn](https://www.linkedin.com/company/storagereview-com) [YouTube](https://www.youtube.com/user/storagereview?sub_confirmation=1) [Email](mailto:info@storagereview.com) [Spotify](https://open.spotify.com/show/1y6VnznABhHeOSMOmbDTz0) [Reddit](https://www.reddit.com/r/StorageReview/) [Discord](https://discord.gg/TwMHb4azdC) [RSS Feed](https://www.storagereview.com/rss.xml) [TikTok](https://www.tiktok.com/@storagereview) [Facebook](https://www.facebook.com/@storagereview) [X (Twitter)](https://twitter.com/storagereview) [Instagram](https://www.instagram.com/storagereview/) [LinkedIn](https://www.linkedin.com/company/storagereview-com) [YouTube](https://www.youtube.com/user/storagereview?sub_confirmation=1) [Email](mailto:info@storagereview.com) [Spotify](https://open.spotify.com/show/1y6VnznABhHeOSMOmbDTz0) [Reddit](https://www.reddit.com/r/StorageReview/) [Discord](https://discord.gg/TwMHb4azdC) [RSS Feed](https://www.storagereview.com/rss.xml) [TikTok](https://www.tiktok.com/@storagereview) [![StorageReview.com](https://www.storagereview.com/wp-content/uploads/2026/07/Storage-Review-2x.png)](https://www.storagereview.com) ≡ Menu - [Home](https://www.storagereview.com/) - [Storage Reviews](https://www.storagereview.com/review) - [End User Reviews](https://www.storagereview.com/consumer) - [Enterprise Reviews](https://www.storagereview.com/enterprise) - [Ubiquiti Reviews](https://www.storagereview.com/best/ubiquiti-reviews) - [SR Merch](https://store.storagereview.com) - [Leaderboards](https://www.storagereview.com/best) - [Best Storage Arrays](https://www.storagereview.com/best/storage-arrays) - [Best Enterprise SSDs](https://www.storagereview.com/best/enterprise-ssds) - [Best Servers](https://www.storagereview.com/best/servers) - [Best Enterprise GPUs](https://www.storagereview.com/best/enterprise-gpus) - [Best Desktops for Local AI](https://www.storagereview.com/best/desktops-local-ai) - [Best Laptops for Local AI](https://www.storagereview.com/best/laptops-local-ai) - [Best Local LLM Tools](https://www.storagereview.com/best/local-llm-tools) - [Agentic AI Hardware](https://www.storagereview.com/best/agentic-ai-hardware) - [Best SSDs & Hard Drives](https://www.storagereview.com/best_drives) - [Best Portable SSDs](https://www.storagereview.com/best/portable-ssds) - [Best Business Laptops](https://www.storagereview.com/best/business-laptops) - [Best Mobile Workstations](https://www.storagereview.com/best/mobile-workstations) - [Best Desktop Workstations](https://www.storagereview.com/best/desktop-workstations) - [Best Mini PCs](https://www.storagereview.com/best/mini-pcs) - [Best Laptop Battery Life](https://www.storagereview.com/best/laptop-battery-life) - [Storage Reference Guide](https://www.storagereview.com/storage-reference-guide) - [About SR](https://www.storagereview.com/about-storagereview) - [StorageReview.com Sweepstakes Rules and Regulations](https://www.storagereview.com/storagereview-com-sweepstakes-rules-and-regulations) Search [Home](https://www.storagereview.com/) » [News](https://www.storagereview.com/news) » High Bandwidth Flash Gets Its First Open Spec: 512GB Stacks and Up to 3.0TB/s # High Bandwidth Flash Gets Its First Open Spec: 512GB Stacks and Up to 3.0TB/s by Brian Beeler on August 4, 2026 [Enterprise](https://www.storagereview.com/enterprise)  ◇  [SSD](https://www.storagereview.com/enterprise/ssd) Sandisk and SK hynix have released the first HBF (High Bandwidth Flash) technical specification through the Open Compute Project, six months after the two companies formed the HBF workstream in February. Google and Tenstorrent joined the consortium during the standardization process, and the spec is now openly available to any company designing AI inference systems or accelerators. HBF is a NAND-based answer to a DRAM problem. AI inference wants high-bandwidth memory close to compute, but HBM capacity is limited and expensive, while model sizes and context windows keep growing. HBF slots between the two extremes: flash-based stacks that trade some of HBM’s speed for far greater capacity and persistence, giving system designers a tier for model weights and long-context data that no longer fits in DRAM but cannot live on an SSD. The specification puts real numbers behind the concept. Per SK hynix, HBF stacks come in 8-high and 16-high NAND configurations at up to 512GB per stack, with three performance grades spanning 0.4TB/s to 3.0TB/s, connected over the UCIe standard. The document defines the xPU-HBF host interface, electrical guidelines, baseline performance expectations, reliability and packaging guidance for an HBF die stack, and a software user guide for read and write operations. The companies designed the spec so HBF can coexist with HBM in the same system rather than replace it.![Diagram of High Bandwidth Flash as a new memory tier between HBM and SSDs, with figures from the first HBF specification](https://www.storagereview.com/wp-content/uploads/2026/08/StorageReview-Sandisk-HBF-Memory-Tier-2.png) Sandisk and SK hynix are explicit about the strategy: publish early and openly through OCP to position HBF as the de facto standard for the AI storage market before rivals define an alternative. “AI inference is creating a new set of memory requirements, and HBF technology is designed to meet that moment,” said Alper Ilkbahar, chief technology officer at Sandisk, calling the spec a milestone “for the next generation of AI systems built to improve token economics at scale.” The capacity math is the same one driving [KV cache offload to flash](https://www.storagereview.com/review/the-token-efficient-path-for-long-context-inference-kv-cache-offload-to-flash): keeping context in a cheaper, denser tier raises how many tokens and users each accelerator can serve. ## BiCS10 QLC Claims the Density Crown Sandisk’s other FMS announcement came with Kioxia: BiCS10 QLC, the pair’s tenth-generation quad-level-cell 3D NAND. The companies say the new die delivers a 60% bit density increase over their 8th-generation QLC and, at more than 37Gb/mm², the industry’s highest bit density for QLC NAND. It carries the same 332 active layers as the [BiCS10 TLC die that began sampling in July](https://www.storagereview.com/news/sandisk-and-kioxia-begin-sampling-332-layer-bics10-3d-nand), built on the same CBA (CMOS directly Bonded to Array) process that manufactures logic and memory array on separate wafers before bonding them. On the interface side, BiCS10 QLC runs Toggle DDR6.0 at 4.8Gb/s with a Separate Command Address protocol, and adds Power-Isolated Low-Tapped Termination to improve data-out transfer efficiency. “Our 10th-generation QLC 3D flash memory delivers simultaneous gains in density, bandwidth, and energy efficiency,” Ilkbahar said, while Kioxia CTO Hideshi Miyajima pointed at the target market: efficiently storing rapidly expanding data volumes for AI systems. Neither company gave a sampling date for the QLC die.![Kioxia and Sandisk BiCS10 QLC NAND key specifications: 60 percent density gain, 37Gb per square millimeter, 332 layers, 4.8Gb/s interface]() ## Keynote Wednesday, Memory Wall Panel Thursday Sandisk’s FMS keynote, “NAND: The Versatile & Scalable Foundation of the AI Era,” runs Wednesday, August 5 at 11:40 a.m. PT, presented by chief revenue officer Jim Elliott, chief product officer Khurram Ismail, and Ilkbahar. On Thursday at 9:45 a.m. PT, Sandisk, SK hynix, and Google share a panel titled “Breaking the Memory Wall with High Bandwidth Flash,” moderated by Tom Coughlin, digging into architectural integration, standardization timelines, and the economics of the new tier. Sandisk is showing HBF, next-generation NAND, enterprise SSDs, and its updated AI Data Cycle framework at booth #607. The spec release comes in a week thick with memory-hierarchy news; [Samsung used its own FMS keynote](https://www.storagereview.com/news/samsung-outlines-3d-memory-roadmap-for-ai-infrastructure-at-fms-2026) to preview zHBM and zNAND-O concepts aimed at the same AI inference wall. The difference is that HBF now has a published, open specification behind it, and with Google and Tenstorrent already in the consortium, the standards race for flash-as-memory has a front-runner. All figures above are vendor-stated; we hope to see HBF hardware in the lab before anyone ships production systems built on it. **Engage with StorageReview** [Newsletter](https://www.storagereview.com/storage_newsletter) |  [YouTube](https://www.youtube.com/user/StorageReview "Opens in a new window") | Podcast  [iTunes](https://podcasts.apple.com/gb/podcast/storagereview-com-storage-reviews/id1060681115 "Opens in a new window")/ [Spotify](https://open.spotify.com/show/1y6VnznABhHeOSMOmbDTz0 "Opens in a new window") |  [Instagram](https://www.instagram.com/storagereview/ "Opens in a new window") |  [Twitter](https://twitter.com/storagereview "Opens in a new window") |  [TikTok](https://www.tiktok.com/@storagereview? "Opens in a new window") |  [RSS Feed](https://www.storagereview.com/rss.xml) ![]() ### Brian Beeler Brian is located in Cincinnati, Ohio and is the chief analyst and President of StorageReview.com. 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