by Anton Shilov
10/13/2009 | 09:00 AM
SanDisk Corp., one of the world's largest suppliers of flash-based products, said on Tuesday that it had started commercial shipments of multi-level cell (MLC) flash memory that can store four bits of data per single flash cell. The chips are made by Toshiba Corp. using 43nm process technology.
The first products based on the 64Gb "X4" NAND flash chips are 8GB and16GB SDHC cards as well as 8GB and 16GB Memory Stick Pro Duo. The 4-bits-per-cell technology allows SanDisk to make the novelties very cost-effective, something crucially important on the highly-competitive market of flash-based devices.
But multi-bit-per-cell technologies allow to make flash memory much cheaper to manufacture, multi-level-flash memory is less reliable compared to single-level-cell (SLC) flash in terms of mean time before failure (MTBF). As a result, developers of flash memory have to implement numerous technologies to ensure sufficient lifespan and the lack of errors. SanDisk claims that its 4bpc memory incorporates a number of its technical know-hows.
"The development and commercialization of X4 technology represents an important milestone for the flash storage industry. Our challenge with X4 technology was to not only deliver the lower costs inherent to 4-bits-per-cell, but to do so while meeting the reliability and performance requirements of industry standard cards that employ MLC NAND. Our world-class design and engineering team has applied its deep experience with high speed 2 and 3-bits-per-cell flash chip designs and collaborated closely with our leading design partners to develop and perfect new and powerful error correction algorithms to assure reliable operation,"said Sanjay Mehrotra, president and chief operating officer of SanDisk.
SanDisk's advanced X4 controller, which is necessary to effectively manage the complexities and performance requirements of X4 memory utilizes a first-of-its-kind error correcting code (ECC) scheme specifically developed for use in storage systems, and tailored to support the 16 levels of distribution needed for 4-bits-per-cell.
The first X4 flash memory chips boast with 7.8MB/s memory write performance, which is comparable with current multi-level cell technologies. SanDisk’s patented All-Bit-Line (ABL) architecture as well as the newly introduced three-step programming (TSP) and sequential sense concept (SSC) serve as key enablers to X4’s impressive performance.