SanDisk working on 3bit per cell NAND for SSDs

SanDisk announced at a press conference in Tokyo that it plans to NAND flash memory chips for solid state disks that can store three bits per cell, which is one bit more per cell than current NAND flash memory. These new chips will make SSDs cheaper, while boosting the storage capacity as well. There are still some problems with the read/write speeds, but the first SSDs with 3-bit per cell memory should arrive sometime in 2009 or 2010.

SanDisk is ahead of its rival manufacturers in miniaturization and multiple level cell (MLC) technologies, which hold the key to reducing NAND flash memory cost. The company has already started to mass-produce its 56nm 3bit/cell product and 43nm 2bit/cell product, planning the volume production of its 43nm 3 to 4bit/cell products at the end of 2008. And it will advance the process technology to 3Xnm in the second half of 2009.

SanDisk also unveiled a bit more information about their upcoming ExtremeFFS file management system for solid state disk which will arrive in 2009 with 2-bit per cell NAND flash memory. SanDisk says the new file system can boost write speeds by up to 100x, while increasing rewrite endurance as well.

With the ExtremeFFS, SanDisk improved its file management technology in the following three respects. First, the new system can manage data by page unit, which is a smaller data storage unit compared with the prior block unit.

Second, it can perform different actions in parallel via multiple channels. For example, while the user is writing data and doing "garbage collection" (liberating unused memory) via one channel, data can be read out via a different channel.

Third, the new system can "learn" the user's pattern of using data and localize data storage areas in accordance with factors including how often the data has been used.