Samsung has confirmed its 4bit/cell flash is incoming – that's a QLC (quad-level cell) NAND chip.
The highest capacity flash cells right now are TLC (triple-level cell) with 3 bits/cell. It's harder to make QLC flash as the stuff has slower read and write times than TLC and less endurance at die level. Read a QLC flash primer here.
SSDs could be built with parallel access to many dies to help access speed, and also over-provisioning to extend endurance.
So far Toshiba and foundry partner WDC have been making the QLC running, with a 768Gbit die. Unless their joint venture implodes through their antipathy concerning Toshiba's sale of its interests then that chip should also appear next year.
A Samsung staffer told Business Korea: "QLC NAND flash is not yet in mass production, but we are preparing it internally." It is being built with Samsung's V-NAND (3D NAND) technology and a 1Tb (128GB) die size could be produced. It may use the fifth version of Samsung's V-NAND technology. As gen 4 is 64-layer V-NAND then gen 5 could be 96-layer.
Samsung has previously talked about a 128TB QLC SSD in a 2.5-inch form factor.
SK Hynix is also preparing QLC flash chips.
QLC flash should arrive in the first 2018 quarter, according to IHS Markit, which thinks it may achieve a 5.1 per cent market share by the end of 2018 and a 30 per cent share in 2021.
If QLC pricing is significantly lower than TLC then new use cases may open up, such as high-capacity and fast-access nearline flash, and low-access latency archival or object storage. ®