Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second (MB/s), megabits per second (Mbit/s), or in optical drive multipliers such as "180X" (180 times 150 KiB/s).[19] File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30 MB/s and write at about half that rate, which was about 20 times faster than the theoretical transfer rate achievable by the previous model, USB 1.1, which is limited to 12 Mbit/s (1.5 MB/s) with accounted overhead.[20] The effective transfer rate of a device is significantly affected by the data access pattern.[21]
Hardware designers later developed EEPROMs with the erasure region broken up into smaller "fields" that could be erased individually without affecting the others. Altering the contents of a particular memory location involved copying the entire field into an off-chip buffer memory, erasing the field, modifying the data as required in the buffer, and re-writing it into the same field. This required considerable computer support, and PC-based EEPROM flash memory systems often carried their own dedicated microprocessor system. Flash drives are more or less a miniaturized version of this.
The various writable and re-writable forms of CD and DVD are portable storage media supported by the vast majority of computers as of 2008. CD-R, DVD-R, and DVD+R can be written to only once, RW varieties up to about 1,000 erase/write cycles, while modern NAND-based flash drives often last for 500,000 or more erase/write cycles. DVD-RAM discs are the most suitable optical discs for data storage involving much rewriting.
M-Systems, an Israeli company, were granted a US patent on November 14, 2000, titled "Architecture for a [USB]-based Flash Disk", and crediting the invention to Amir Ban, Dov Moran and Oron Ogdan, all M-Systems employees at the time. The patent application was filed by M-Systems in April 1999.[6][1][7] Later in 1999, IBM filed an invention disclosure by one of its employees.[1] Flash drives were sold initially by Trek 2000 International, a company in Singapore, which began selling in early 2000. IBM became the first to sell USB flash drives in the United States in 2000.[1] The initial storage capacity of a flash drive was 8 MB.[7] Another version of the flash drive, described as a pen drive, was also developed. Pua Khein-Seng from Malaysia has been credited with this invention.[8] Patent disputes have arisen over the years, with competing companies including Singaporean company Trek Technology and Chinese company Netac Technology, attempting to enforce their patents.[9] Trek won a suit in Singapore,[10][11] but has lost battles in other countries.[12] Netac Technology has brought lawsuits against PNY Technologies,[13] Lenovo,[14] aigo,[15] Sony,[16][17][18] and Taiwan's Acer and Tai Guen Enterprise Co.[18]
A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case, which can be carried in a pocket or on a key chain, for example. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing connection with a port on a personal computer, but drives for other interfaces also exist. USB flash drives draw power from the computer via the USB connection. Some devices combine the functionality of a portable media player with USB flash storage; they require a battery only when used to play music on the go.
The 32GB capacity of this SanDisk Ultra SDCZ48-032G-A46 flash drive provides ample room to store photos, music, videos and other files. The USB 3.0 interface and up to 80MB/sec. read speed make it easy to transfer files to and from your computer. (Ten times faster than USB 2.0 drives. Write speeds up to 10 times faster than Cruzer USB 2.0 drive.)* *USB 3.0 port required. Based on internal testing; performance may be lower depending upon host device.
Many types of USB drive, sometimes referred to as a thumb drive, also have handy features like a key chain ring or a small LED flashlight. Some can even transmit your data wirelessly for the ultimate in digital convenience. And as with any fun accessory, there are plenty of novelty versions of flash drives designed to show your personality, display your sense of humor, or broadcast your team loyalty.
