Solidigm showed a working prototype of SSD on the NAND PLC

Solidigm showed a working prototype of SSD on the NAND PLC

Solidigm, a former Intel flash memory company owned by SK Hynix, presented a working prototype of SSD at the Flash Memorial 2022 event on a new flash memory type, the NAND. This flash memory technology allows five bits of information to be stored in a cell, providing a higher density of memory chips.

The NAND PLC allows more data to be stored than all common flash memory options: QLC and the widespread introduction of II-algorithms, the need for larger and faster data storage facilities will increase. Under these conditions, the PLC flash memory technology, which, compared to QLC NAND, allows a 25% increase in data on a semiconductive crystal of the same area, can be a suitable tool for scaling up the storage capacity of solid storage devices.

As is known, the elementary units of information measurement are bits with "zero" and "unit" states, which in the case of SSD are recorded in the NAND cell. In comparison with QLC NAND, the PLC technology adds additional states to the cells that add another bit of information. For example, the PLC memory technology uses 32 cell states that cover all possible combinations of five units and zeros.

However, the more states a cell can accept, the higher the load on the cell itself, as well as on the SSD memory controller, which should read these states. This increases the probability of incorrect recording or reading, which in turn may result in damage to the data. To compensate for these risks at the SSD controller level, better error correction algorithms must be used. In the case of a PLC NAND, the accuracy requirements for these algorithms are multiplied.

The increase in the number of possible cell states also affects the life expectancy of the cells. The reduction in the expected life expectancy of the NAND cells as data storage density increases is one of the reasons why solid storage devices, even on the QLC NAND base, are considered less reliable than models built on the NAND TLC.

But since Solidigm's PLC NAND is based on Intel technology, it uses a different cell architecture from those used by other NAND memory chip manufacturers. Its flash memory is built on transistors with floating closures, which, according to Solidigm, are much better suited to increasing the number of bits stored in cells than the commonly used charge traps.

At present, it is not known when the first commercial products on the NAND PLC market will be available. Previously, Western Digital predicted that this would not happen until 2025.