Supercomputer

BackgroundEdit

The origins of flash memory can be traced back to the development of the floating-gate MOSFET (FGMOS), also known as the floating-gate transistor. The original MOSFET (metal-oxide-semiconductor field-effect transistor), also known as the MOS transistor, was invented by Egyptian engineer Mohamed M. Atalla and Korean engineer Dawon Kahng at Bell Labs in 1959.[6] Kahng went on to develop a variation, the floating-gate MOSFET, with Simon Min Sze at Bell Labs in 1967 They proposed that it could be used as floating-gate memory cells for storing a form of programmable read-only memory (PROM) that is both non-volatile and re-programmable
Early types of floating-gate memory included EPROM (erasable PROM) and EEPROM (electrically erasable PROM) in the 1970s However, early floating-gate memory required engineers to build a memory cell for each bit of data, which proved to be cumbersome,[8] slow,[9] and expensive, restricting floating-gate memory to niche applications in the 1970s, such as military equipment and the earliest experimental mobile phones.

Invention and commercializationEdit

Fujio Masuoka, while working for Toshiba, proposed a new type of floating-gate memory that allowed entire sections of memory to be erased quickly and easily, by applying a voltage to a single wire connected to a group of cells.[4] This led to Masuoka's invention of flash memory at Toshiba in 1980.[8][10][11] According to Toshiba, the name "flash" was suggested by Masuoka's colleague, Shōji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera . Masuoka and colleagues presented the invention of NOR flash in 1984. and then NAND flash at the IEEE 1987 International Electron Devices Meeting (IEDM) held in San Francisco.
Toshiba commercially launched NAND flash memory in 1987. Intel Corporation introduced the first commercial NOR type flash chip in 1988 NOR-based flash has long erase and write times, but provides full address and data buses, allowing random access to any memory location. This makes it a suitable replacement for older read-only memory (ROM) chips, which are used to store program code that rarely needs to be updated, such as a computer's BIOS or the firmware of set-top boxes. Its endurance may be from as little as 100 erase cycles for an on-chip flash memory,[17] to a more typical 10,000 or 100,000 erase cycles, up to 1,000,000 erase cycles.[18] NOR-based flash was the basis of early flash-based removable media; CompactFlash was originally based on it, though later cards moved to less expensive NAND flash.
NAND flash has reduced erase and write times, and requires less chip area per cell, thus allowing greater storage density and lower cost per bit than NOR flash; it also has up to 10 times the endurance of NOR flash. However, the I/O interface of NAND flash does not provide a random-access external address bus. Rather, data must be read on a block-wise basis, with typical block sizes of hundreds to thousands of bits. This makes NAND flash unsuitable as a drop-in replacement for program ROM, since most microprocessors and microcontrollers require byte-level random access. In this regard, NAND flash is similar to other secondary data storage devices, such as hard disks and optical media, and is thus highly suitable for use in mass-storage devices, such as memory cards and solid-state drives (SSD). Flash memory cards and SSDs store data using multiple NAND flash memory chips. The first NAND-based removable memory card format was SmartMedia in 1995, and many others have followed, including:

• 
  MultiMediaCard
  
• 
  Secure Digital
  
• 
  Memory Stick, and xD-Picture Card.