Kioxia’s new 5TB, 64 GB/s flash module puts NAND toward the memory bus for AI GPUs — HBF prototype adopts familiar SSD form factor

Kioxia has developed a prototype of the 5TB high-bandwidth flash memory module with a bandwidth of 64 GB/s. It’s essentially NAND-based memory for GPUs. Compared to HBM, High Bandwidth Flash (HBF) adapts the concept to NAND flash, offering 8-16x the capacity of DRAM-based HBM. By combining speed with persistent storage, HBF enables large AI datasets to be accessed efficiently while using less power. One of these HBF modules, which Kioxia has pushed to 64 GB/s, is what allows this capability.

When you hear “flash storage,” you usually think in terms of capacity first, speed second. Even the fastest PCIe 5.0 SSDs today—14 GB/s class drives like Samsung’s 9100 Pro—are dwarfed by the bandwidth demands of modern GPUs and CPUs. Kioxia’s new prototype turns that expectation on its head: a single flash module delivering 5 TB of capacity and 64 GB/s of sustained bandwidth over PCIe 6.0. To put that into perspective, that’s over 4x faster than the fastest PCIe 5.0 drives shipping today, and within striking distance of HBM2E’s per-stack throughput.

The key is how the system scales; instead of one central controller trying to manage an entire bank of NAND—which quickly becomes a bottleneck as more dies and channels are added—Kioxia gives each module its own controller. That controller sits right next to its NAND and links to others in a daisy-chain layout. This reduces crosstalk and eliminates the complexity of wide parallel buses, which become increasingly challenging to manage as speeds increase. Instead, data is passed along in series, with each link pushing 128 Gbps using PAM4 signaling.

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PAM4 (Pulse Amplitude Modulation with four levels) doubles the data rate per symbol compared to traditional NRZ signaling, but it’s also more sensitive to noise and bit errors. To maintain signal integrity, Kioxia relies on equalization, error correction, and stronger pre-emphasis—similar to what PCIe 6.0 itself requires.