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Flash Memory: Theory and Applications
The Flash memory was invented by
Dr. Fujio Masuoka while working for Toshiba in 1984. According to Toshiba, the
name 'Flash' was suggested by Dr. Masuoka's colleague, Mr. Shoji Ariizumi,
because the erasure process of the memory contents reminded him of a flash of a
camera. Dr. Masuoka presented the invention at the IEEE 1984 Integrated
Electronics Devices Meeting held in San Jose, California. Intel saw the massive
potential of the invention and introduced the first commercial NOR type flash
chip in 1988.
NOR-based flash has long erase
and write times, but has a full address/data (memory) interface that allows
random access to any location. This makes it suitable for storage of program
code that needs to be infrequently updated, such as a computer's BIOS or the
firmware of set-top boxes. Its endurance is 10,000 to 1,000,000 erase cycles.
NOR-based flash was the basis of early flash-based removable media; Compact
Flash was originally based on it, though later cards moved to the cheaper NAND
flash.
NAND flash from Samsung and
Toshiba followed in 1989. It has faster erase and write times, higher density,
and lower cost per bit than NOR flash, and ten times the endurance. However its
I/O interface allows only sequential access to data. This makes it suitable for
mass-storage devices such as PC cards and various memory cards, and somewhat
less useful for computer memory.
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