Flash Memory - Capacity

Capacity

Multiple chips are often arrayed to achieve higher capacities for use in consumer electronic devices such as multimedia players or GPSs. The capacity of flash chips generally follows Moore's Law because they are manufactured with many of the same integrated circuits techniques and equipment.

Consumer flash storage devices typically are advertised with usable sizes expressed as a small integral power of two (2, 4, 8, etc.) and a designation of megabytes or gigabytes (e.g., 512 MB, 8 GB). "MB" and "GB" here (and on the device packaging) are using "decimal prefixes," meaning 1,000,000 bytes and 1,000,000,000 bytes, respectively. This includes SSDs marketed as hard drive replacements, in accordance with traditional hard drives, which also use decimal prefixes. Thus, an SSD marked as "64 GB" is actually at least 64 × 1,0003 bytes (64 GB), or often a bit more. Most users will have slightly less capacity than this available for their files, due to the space taken by file system metadata.

The flash memory chips inside them are sized in strict binary multiples, but the actual total capacity of the chips is not usable at the drive interface. It is considerably larger than the advertised capacity in order to allow for distribution of writes (wear leveling), for sparing, for error correction codes, and for other metadata needed by the device's internal firmware.

In 2005, Toshiba and SanDisk developed a NAND flash chip capable of storing 1 GB of data using multi-level cell (MLC) technology, capable of storing two bits of data per cell. In September 2005, Samsung Electronics announced that it had developed the world’s first 2 GB chip.

In March 2006, Samsung announced flash hard drives with a capacity of 4 GB, essentially the same order of magnitude as smaller laptop hard drives, and in September 2006, Samsung announced an 8 GB chip produced using a 40 nm manufacturing process. In January 2008, Sandisk announced availability of their 16 GB MicroSDHC and 32 GB SDHC Plus cards.

More recent flash drives (as of 2012) have much greater capacities, holding 64, 128, and 256 GB. Some of the larger drives, due to their size, can be used for full computer backups.

There are still flash-chips manufactured with capacities under or around 1 MB, e.g., for BIOS-ROMs and embedded applications.

Read more about this topic:  Flash Memory

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