An all-electronic storage device that is an alternative to a hard disk drive. Also called a "solid state disk" and "electronic disk." Employed in myriad products, such as smartphones, MP3 players, digital cameras and laptop computers, solid state drives (SSDs) are faster than hard disks because there is zero latency (no read/write head to move). They are also more rugged and offer greater protection in hostile environments.
Non-Volatile Flash and Volatile DRAM
The great majority of solid state drives use flash memory chips, and as flash memory becomes less costly, the storage capacity increases. Like a hard disk, flash memory is non-volatile and holds its content without power. In contrast, there are solid state drives that use volatile DRAM or SRAM chips, which are backed up by a built-in hard disk or UPS in case of power failure (see nvSRAM and BBSRAM).
It will take some time, but eventually, spinning disk platters will be as obsolete as the punch card (see future memory chips). There are also hybrid solid state drives that use both memory and magnetic disk platters (see hybrid drive). See disk on module and garbage collection.
An SSD emulates the sector format of a hard disk and is generally a plug-for-plug replacement for it, such as this BITMICRO drive. BITMICRO makes SSDs from 8GB to over a terabyte that can withstand up to 1,500 Gs of operating shock. (Image courtesy of BITMICRO Networks, Inc., www.bitmicro.com)
RAM chips provide the fastest access times. This earlier MegaRAM unit contained 4GB of dynamic RAM and a hard disk. In case of power failure, the battery enabled the RAM to be copied to the disk (see
PC Cards were the first plug-in format for solid state drives. These 40 and 175MB FLASHDISKs, next to a CompactFlash card for size comparison, are minuscule today but provided much-needed, extra storage for early laptops. (Image courtesy of SanDisk Corporation, www.sandisk.com)
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