What is NAND Flash?
NAND flash is a form of non-volatile memory introduced by Toshiba and Samsung in 1989. Its benefits include high storage density, fast access times, low power requirements in operation, and excellent shock resistance. These benefits are tempered somewhat by the inherent limitations of the technology: • Due to production yield constraints, NAND flash ships from the factory with a number of bad blocks that cannot be used. • NAND flash has a serialized data interface similar to a hard disk and so cannot be used for execute in place functionality, such as running code directly from the chip. • Over time and after multiple erase cycles the memory will tend to “wear” and become less reliable. • The bits stored in the chip can sometimes flip – or reverse – from 0 to 1 or vice versa. Over time, NAND flash technology and software has evolved to the point where these limitations are invisible to the end user. Owners of iPod Nanos do not overly concern themselves with bad blocks or bit-flipping.
