The Intel SSD 660p SSD Review: QLC NAND Arrives For Consumer SSDs

KONTAK PERKASA FUTURES - When NAND flash memory was first used for general purpose storage in the earliest ancestors of modern SSDs, the memory cells were treated as simply binary, storing a single bit of data per cell by switching cells between one of two voltage states. Since then demand for higher capacity has pushed the industry to store more bits in each flash memory cell.

KONTAK PERKASA FUTURES - In the past year, the deployment of 64-layer 3D NAND flash has allowed almost all of the SSD industry to adopt three bit per cell TLC flash, which only a few short years ago was the cutting edge. Now, four bit per cell, also known as Quad-Level Cell (QLC) NAND flash, is the current frontier.

KONTAK PERKASA FUTURES - Each transition to storing more bits per memory cell comes with significant downsides that offset the appeal of higher storage density. The four bits per cell storage mode of QLC requires discriminating between 16 voltage levels in a flash memory cell. The process of reading and writing with adequate precision is unavoidably slower than accessing NAND flash that stores fewer bits per cell. The error rates are higher, so QLC-capable SSD controllers need very robust error correction capabilities. Data retention and write endurance are reduced.

But QLC NAND is entering a market where TLC NAND can provide more performance and endurance than most consumers really need. QLC NAND doesn't introduce any fundamentally new problems, it just is afflicted more severely with the challenges that have already been overcome by TLC NAND. The same strategies that are in widespread use to mitigate the downsides of TLC NAND are also usable for QLC NAND, but QLC will always be the cheaper lower-quality alternative to TLC NAND.

On the commercial product front, Micron introduced an enterprise SATA SSD with QLC NAND this spring, and everyone else is working on QLC NAND as well. But for consumers, where the pricing advantages of QLC are going to be the most noticed, it is Intel who the first to market with a consumer SSD that uses QLC NAND flash memory. Today the company is taking the wraps off of their new Intel SSD 660p, an entry-level M.2 NVMe SSD with up to 2TB of QLC NAND.

Intel has reportedly cut off further development of consumer SATA drives, so naturally their first consumer QLC SSD is a member of their 6-series, the lowest tier of NVMe SSDs. The 660p comes as a replacement for the Intel SSD 600p, Intel's first M.2 NVMe SSD and one of the first consumer NVMe drives that aimed to be cheaper and slower than the premium high-end NVMe SSDs, through the use of TLC NAND at a time when NVMe SSDs were still primarily using MLC NAND. The purpose of the Intel 660p is to push prices down even further while still providing better performance than SATA SSDs or the 600p.

Source : anandtech.com