Western Digital’s about to be spun-off Sandisk business unit held an investor day session and revealed details of three new SSDS coming later this year along with plans for High-Bandwidth Flash (HBF), a NAND equivalent of high-bandwidth DRAM (HBM).
It needs to reassure investors that it’s a solid business ahead of the spinout. As part of this effort, Sandisk execs presented their view of the market, technology trends, and product strategies to show that its technology will appeal to customers and remain relevant.
Sandisk’s latest 3D NAND generation is called BiCS8, it has 218 layers and is used to make a 2Tb QLC die, which is said to be the world’s highest capacity NAND die in production. Sandisk previewed a future BiCS generation with more than 300 layers. It will be used to make a 1Tb TLC die. Generally speaking WD/Sandisk uses TLC NAND for performance drives and QLC NAND for capacity-centric drives. It showed a slide predicting QLC’s growing presence in the client SSD market, and also the deepening penetration of PCIe gen 5:
This will feed into the first new drive, a PC QLC product with 512GB, 1TB and 2TB capacity levels, using a PCIe gen 4 interconnect.
This capacity-focused drive will ship later this year as will a performance-centered PC gen 5 product using faster TLC NAND and coming with with 512GB, 1TB, 2TB and 4TB capacity levels. There is initial performance data on the slide image above.
A capacity-centric datacenter drive was also previewed, the UltraQLC DC SN670:
The UltraQLC angle refers to the controller having hardware accelerators, being scalable to the 64 Die/Channel level, able to scale power according to workload demand and including an “integrated advanced toggle mode bus Mux control.” Toggle mode NAND uses a double data rate interface for faster data transfers and a multiplexer (Mux) manages the data lanes. Sandisk’s version of this technology will be managing the NAND-SSD controller data flow more efficiently.
The SN670 uses the PCIe gen 5 bus and will have either 64TB or128TB capacities, meaning 61.44TB or 122.88TB usable respectively. It is scheduled ship in the third quarter of 2025. Both Solidigm and Phison announced 122.88TB SSDs in November last year.
Sandisk displayed a capacity eSSD progression slide with 128TB in calendar 2025, 256TB in 2026, 512TB in 2027 and 1PB after that but with no year identified.
On the future technology front, Sandisk talked about 3D Matrix Memory (DRAM) to help solve the memory wall problem; the growing disparity between memory capacity and bandwidth. It’s working with IMEC on this technology with a CMOS development project with 4-8Gbit capacity.
It is also developing bandwidth-optimised NAND with its HBF concept, which it suggests could provide equivalent HBM bandwidth with 8 to 16 times HBM capacity at the same cost.
In effect stacked HBM DRAM layers would be replaced in whole or part by NAND layers, connecting to a host GPU/CPU/TPU via a logic die and an interposer. An 8-high stack could have 6 x 512GB NAND dies and 2 HBM ones to provide 3.12PB of total capacity, which compares to an 8Hi HBM chip with 192GB of total capacity.
An all-HBF 8Hi stack would have 4PB of capacity. Sandisk said a c1.8 trillion parameter LLM with 16-bit weights needs 3.6PB of memory and could fit in an 8Hi HBF chip. If we envisage an LLM running on a smartphone then a 64 billion parameter MoE model could fit inside an HBF chip in the phone. It foresees 3 HBF generations with gen 2 having 1.5x the capacity of gen 1 and 1.45x the read bandwidth, and gen 3 being 2x gen in both categories. The energy efficiency would also improve generation by generation.
HBF is not drop-in compatible with HBM but does have the same electrical interface “with minor protocol changes.”
Sandisk wants to help form an open HBF standard ecosystem and is setting up a technical advisory board “of industry luminaries and partners.”
If the HBF idea spreads, with Micron, Samsung and/or SK hynix adopting it, then we could have a near-storage-class memory concept. Download the full Sandisk investor day slide set here.
