Hardware Reference
In-Depth Information
Chapter 10. Flash and Removable Storage
Alternative Storage Devices
Since the mid-1980s, the primary storage device used by computers has been the hard
disk drive. More recently, however, flash-based storage including SSDs (solid-state drives)
are increasingly being used as hard drive replacements. Although SSDs can physically re-
place a hard disk drive (HDD), they operate using a completely different set of principles
that may require a treatment unlike that used for conventional HDDs. For data backup,
data transport between computers, and temporary storage, secondary removable storage
devices such as flash memory devices/drives, optical drives, magnetic tape drives, remov-
able media hard drives, and even floppy drives have been useful supplements to primary
storage. Optical storage, such as CD, DVD, and BD (Blu-ray Disc), is covered in
Chapter
11
,
“
Optical Storage
.
”
Flash Memory Devices
Flash memory is a special type of solid-state memory chip that requires no power to main-
tain its contents. Flash memory cards can easily be moved from digital cameras to laptop
or desktop computers and can even be inserted into photo printers or self-contained photo
displaydevices.Flashmemorycanstoreanytypeofcomputerdata,butitsoriginalprimary
application was digital photography. However, more and more digital music players have
removableflashmemorycards,andso-called
thumb
or
keychain
flashmemorydevicesthat
plug directly into a USB port have helped make flash memory a mainstream storage medi-
um and a popular replacement for some types of magnetic removable-media storage, par-
ticularlyfloppydisks,Zipdrives,andSuperDiskdrives.FlashmemoryintheformofSSDs
is rapidly increasing in market share as a high-speed alternative to conventional magnetic
hard disk storage.
Flash memory was invented by Fujio Masuoka at Toshiba in the early 1980s, with the ori-
ginalpatents filedinlate1981.AtthetimeToshibaunfortunately didn'tknowhowimport-
ant this invention was, and by 1988 Intel had introduced competitive versions and quickly
took the lead in flash memory development and production.
Flash memory is a type of nonvolatile memory that can be electrically programmed and
erased. It was originally used in PC motherboards as EEPROM (electrically erasable pro-
grammableread-onlymemory)chipsforstoringthemotherboardbasicinput/outputsystem
(BIOS).FlashROMsreplaced theEPROM,whichcouldonlybeprogrammed orerased by
special equipment outside of the motherboard.
