SLC SSDs are rare in the market today, with fewer and fewer MLCs, and TLC has become the absolute mainstream of the market.
January 15, TheReg author, Talked about the future of QLC flash memory and the relationship between 3D NAND , Still very interesting.
As the name implies, QLC is 4bits Cell, which stores higher density signals. In fact, as early as 2009, SanDisk (SanDisk) tried to use the 43nm process QLC flash memory manufacturing, but because of the surprisingly high error rate, had to give up.
The error rate is an unavoidable Flash flash memory of the mountain, the usual approach is to add ECC master control check technology, that is inserted in the data bit parity bit.
Here you understand that the fewer the bits of data, the lower the error rate, so from the storage, SLC is bound to be the most used, followed by MLC, QLC ......
At the same time, the same is true for the process, the more advanced the process, the more the ECC check bit will be, and the more difficult the error correction will be.
SanDisk reason why the erroneous error rate is because the 3D NAND has not developed at this time, based on the 43nm process 2D plane to do the calibration, to the data to achieve a certain accuracy, or capacity is small, or unfinished Huge size
With the maturity of 3D NAND, the future of TLC and even QLC suddenly suddenly opened up.Because of the advantages of 3D structure, a circle around the floating gate as a pillar channel, an increase of 3 times the area, So 30nm made a 90nm effect, error correction greatly reduced the difficulty.
as the picture shows, Also at the 15nm level, MLC flash requires only 50 ECC parity bits, while TLC requires up to 75.
In the era of 3D QLC flash, 20 ECC parity bits are more than enough.
According to Jim Handy, an expert with Objective Analysis, He said PLC flash memory (5bits / Cell) is inevitable, because one of the most obvious fact is that the original 1TB QLC SSD immediately increased to 1.25TB, then 1 yuan 1GB will be possible.
