Flash memory is a form of EEPROM memory, which is Electrically-Erasable Programmable Read-Only Memory. It allows more than one location to be written to and erased in just one operation. Flash memory is what is called non-volatile. That means it does not need power to retain the information that is on the chip itself. Also, flash memory has very fast read access times, though not quite as fast as volatile DRAM which is used as the main memory in PCs. Flash memory, however, is more shock resistant than a computer hard disk drive. It is because of these features that flash memory is so popular in devices such as mobile phones and personal digital assistants.

Flash memory was invented by a gentleman named Fujio Masuoka who was a doctor working for Toshiba in 1984, when he came up with this invention. The name for the memory itself was actually suggested by Dr Masuoka's assistant, Mr. Shoji Ariizumi because he said that the erasure process of the memory contents reminded him of a flash camera. Thus the name flash memory.

Dr. Masuoka presented his invention at the annual IEEE meeting of Integrated Electronics Devices in 1984 that was held in San Jose, California. Intel, one of the biggest manufacturers of computer chips, saw the amazing potential of this invention and unleashed its first NOR type flash chip to the public in 1988.

These chips have very long erase and write times. But their full memory interface allows random access to any location. This makes it perfect for program code storage that doesn't have to be updated frequently such as the BIOS of your computer. It can endure from 10,000 to 1,000,000 erase cycles. NOR based flash was the foundation of early flash based media that could be removed and replaced.

In 1989 NOR flash memory had some company in the form of NAND flash memory. This was developed at both Toshiba and Samsung. The benefits of this type of flash memory over NOR flash memory is that it has faster erase and write times, it's density is higher, and the cost per bit is much lower. It also has ten times the endurance of NOR flash memory. The one drawback is that unlike NOR flash memory which allows random access, NAND flash memory allows only sequential access. This limits its use to mass storage devices like PC cards and memory cards and makes it much less useful for computer memory.

The first NAND removable media format was what was called SmartMedia. After that a number of others followed such as MMC, Secure Digital, Memory Stick, and x-D Picture Cards. Today a new generation of these formats is busting onto the scene with the RS-MMC or Reduced Size Memory Card, The TransFlash, the miniSD, which is a variation of Secure Digital, and the new USB hybrid memory card and intelligent stick. These new formats are very small, usually under 4 centimeters squared.

No doubt the advancements in this type of memory will continue for many years to come. Who knows? Maybe one day our cell phones will be able to fit in a pill box.

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Michael Russell
Your Independent guide to Computer Memory
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