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
Famous quotes containing the word capacity:
“A creative writer must study carefully the works of his rivals, including the Almighty. He must possess the inborn capacity not only of recombining but of re-creating the given world. In order to do this adequately, avoiding duplication of labor, the artist should know the given world.”
—Vladimir Nabokov (1899–1977)
“It is part of the educator’s responsibility to see equally to two things: First, that the problem grows out of the conditions of the experience being had in the present, and that it is within the range of the capacity of students; and, secondly, that it is such that it arouses in the learner an active quest for information and for production of new ideas. The new facts and new ideas thus obtained become the ground for further experiences in which new problems are presented.”
—John Dewey (1859–1952)
“The real security of Christianity is to be found in its benevolent morality, in its exquisite adaptation to the human heart, in the facility with which its scheme accommodates itself to the capacity of every human intellect, in the consolation which it bears to the house of mourning, in the light with which it brightens the great mystery of the grave.”
—Thomas Babington Macaulay (1800–1859)