solid state disk
A disk drive that uses memory chips instead of rotating platters for data storage. Used in battery-powered handheld devices as well as laptop computers, solid state disks (SSDs) are faster than regular disks because there is zero latency (no read/write head to move). They are also more rugged than hard disks and offer greater protection in hostile environments.
Increasingly, solid state technologies are available as a storage option in regular laptops, not just ruggedized ones. It will take some time, but eventually, spinning disk platters will be as obsolete as the punch card (see future memory chips).
Non-Volatile and Volatile
Most solid state disks use non-volatile flash memory; however, some use volatile DRAM or SRAM chips that are backed up by a built-in disk drive or UPS in case of power failure. Also called an "electronic disk," a solid state disk emulates the sector format of a disk drive and is generally a plug-for-plug replacement for it. As memory has gotten less expensive, the storage capacity of solid state devices has increased tremendously. See disk on module, flash disk, dynamic RAM and static RAM.
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| Solid State Disk |
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| BITMICRO makes a complete line of flash memory disks from 128MB to 832GB that are plug-to-plug replacements for IDE/ATA, SATA and SCSI drives in desktop and laptop computers. They can also withstand up to 1,500 Gs of operating shock. (Image courtesy of BITMICRO Networks, Inc., www.bitmicro.com) |
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| RAM-Based Disk |
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| For the ultimate in access time, RAM chips are used in solid state disks. This earlier MegaRAM solid state disk from Imperial Technology held 4GB of volatile RAM and a hard disk. Battery backed, the unit would copy the RAM contents to the hard drive in case of power failure. The company has since offered MegaRAM drives up to one terabyte in capacity. (Image courtesy of Imperial Technology, Inc., www.imperialtechnology.com) |
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| PC Card Disks |
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| PC Cards (PCMCIA) were the first format for solid state disks using flash memory. Although minuscule compared to today's hard disk capacities, these earlier cards provided extra storage for laptops. (Image courtesy of SanDisk Corporation.) |