Quote:The company has also started research into Penta-level cell (PLC) NAND flash and actually verified working five-bit per cell NAND by modifying its current QLC NAND. The new flash provides more density with the ability to store five bits per cell, rather than just four in current QLC. But, to do this, the cell needs to be capable of storing 32 distinct voltage levels, and SSD controllers need to read them back accurately. With so many voltage levels to read to and write at nano-scale, the new technology is very challenging. To get control of the tighter thresholds, the company had to develop some additional processes that may adapt to its current TLC and QLC to boost performance.

QLC is already fairly slow and has lower endurance than other types of flash. PLC will have even less endurance and slower performance. New NVMe protocol features such as Zoned Namespaces (ZNS) should help mitigate some of the issues, however. ZNS by itself aims to reduced write amplification, reduce the need for media over-provisioning and internal controller DRAM usage, and of course, improve throughput and latency.

Quote:Toshiba at the Flash Memory Summit announced they've managed to develop a 5-Bit-per-Cell memory solution Based on its BiCS 4 flash memory technologies, the feat was achieved using a modified module of Quad-Level Cell (QLC) memory. This shows the technology is not only feasible, but has room for improvement, since an adapted QLC technology will always be inferior to a natively-developed, Penta-Level Cell (PLC) solution.

Quote:Intel also announced new SSD 665p manufactured with 96-Layer QLC flash and revealed a roadmap outlining its future Optane SSD products and new 144-Layer QLC NAND. The company also announced that it is working towards developing 5-bit-per-cell flash, otherwise known as penta-level cell (PLC), to offer a path to increased storage density and lower-priced storage.

Quote:Intel announced several new SSDs during its Memory and Storage 2020 event, including the new 3D NAND SSD 670p and the Optane-powered H20 that also comes paired with QLC flash to offer a blend of speed and capacity in a slim package. The company also said that it is on a clear pathway to developing 5-bit-per-cell PLC (Penta-level) flash, allowing the company to replace HDDs for most use-cases.

Intel is at the beginning of a multi-year journey to selling its NAND business to SK hynix. However, the company still plans to operate its SSDs business during the changeover period, and all existing products and support will transfer to SK hynix at the conclusion of the deal in several years. For now, it's business as usual for Intel's storage division, as evidenced by its forward-looking announcement that it is on track to developing PLC flash. However, while the company is obviously bullish on the prospects of PLC, it didn't provide any details of when the new flash will come to market.
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Both the 670p and the H20 use Intel's 144-Layer flash that it fabricates with Micron, and both of Intel's new SSD use density-increasing QLC flash to both reduce cost and boost capacity, though that does come with endurance tradeoffs. Naturally, PLC flash will come with even lower endurance than existing QLC flash, but Intel thinks it's floating gate flash serves as a solid foundation for the new technology.

As we've seen with other SSD vendors, the move to higher-density flash has come coupled with new techniques to provide acceptable levels of endurance, like SLC caching. Intel claims that its floating gate cell design provides superior data retention over the charge trap designs used by its competitors due to superior program/erase voltage thresholds and cell isolation, both of which reduce charge loss over time. The end result is a cheaper, denser flash suitable for use in both consumer and data center applications.

The move to 5-bit-per-cell PLC flash is inevitable, Toshiba announced its intentions to develop the tech back in 2019, and Intel hopes to leverage its floating gate design to enable higher densities while maintaining acceptable performance and endurance characteristics. However, it remains unclear if the new flash will debut while Intel still fabricates its own flash, or if PLC flash will come after the SK hynix takeover.

Intel claims that 5-bit-per-cell PLC flash will help to unseat HDDs on a total cost of ownership (TCO) basis in 2022, but this measurement also factors in the space, power, and cooling costs associated with using a storage device. That means that while PLC SSDs will help SSDs become more competitive with HDDs on an overall cost basis, we likely won't see SSD pricing match HDDs soon.