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What is the difference between NAND and NOR Flash?

What is the difference between NAND and NOR Flash?

Though they are both considered leading non-volatile Flash memory technologies, NAND and NOR Flash meet completely different design needs based on their individual attributes. NOR offers faster read speed and random access capabilities, making it suitable for code storage in devices such as PDAs and cell phones.  However, with NOR technology, write and erase functions are slow compared to NAND.  NOR also has a larger memory cell size than NAND, limiting scaling capabilities and therefore achievable bit density compared to NAND.  Since code storage tends to require lower density memory than file storage, NOR’s larger cell size is not considered a concern when used in these applications.

Conversely, NAND offers fast write/erase capability and is slower than NOR in the area of read speed.  NAND is, however, more than sufficient for a majority of consumer applications such as digital video, music or data storage.  NAND’s fast write/erase speed combined with its higher available densities and a lower cost-per-bit than NOR make it the favored technology for file storage in a host of consumer applications.  Offering users the ability to rewrite data quickly and repeatedly, NAND is typically used for storing large quantities of information in devices such as Flash drives, MP3 players, multi-function cell phones, digital cameras and USB drives. 

The following diagram compares typical NOR and NAND read, program and erase speeds:


1. For purposes of measuring data transfer rate in this context, megabits per second MB/s and/or MBps = 1,000,000 bytes per second.
2. When used herein in relation to memory density, megabit and/or Mb means 1,024x1,024 = 1,048,576 bits.  Usable capacity may be less.  For details, please refer to specifications.
3. When used herein in relation to memory density, gigabit and/or Gb means 1,024x1,024x1,024 = 1,073,741,824 bits.  Usable capacity may be less.  For details, please refer to specifications.


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