Storing Data On Your Computer Chapter 12 Exploring

Storing Data On Your Computer Chapter 12, Exploring the Digital Domain

In this chapter. . . You will learn about n n n how various storage technologies support processing how data is transferred to and from the processor two classes of secondary memory n n n DASD SASD How data is organized on magnetic and optical media

Main Memory n n n RAM is composed of integrated units SDRAM-Synchronous Dynamic RAM DIMMs--Dual Inline Memory Modules

Connecting to the Processor n n a bus is a connection between components classifying buses n n n data width speed early designs featured a single system bus

Connecting to the Processor n n n Modern designs feature two-tier chipset “northbridge”-controller connecting CPU with memory, graphics controller “southbridge”-controller connecting I/O and other devices

Memory Hierarchy I

Memory Hierarchy II

Types of Memory Access n RANDOM ACCESS n n n DIRECT ACCESS n n n items are independently addressed access time is constant items are independently addressed in regions access time is variable—though not significantly SEQUENTIAL ACCESS n n items are organized in sequence (linearly) access time is significantly variable

Secondary Memory n SEQUENTIAL ACCESS STORAGE DEVICES AND MEDIA (SASD) n n magnetic tape DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD) n n n magnetic floppy disks magnetic hard disks optical discs

Direct Access Storage Devices n n n magnetic hard and floppy disks removable hard disks optical discs n n n CD-ROM, CD-RW, DVD GEOMETRY: TRACKS and SECTORS

DASD Media n n n CAV — constant angular velocity (e. g. , floppy and hard disks) CLV — constant linear velocity (e. g. , optical discs) Zoned CAV — number of sectors depends upon zone

Direct Access n n n SEEK — controller advances read/write head to proper track LATENCY — waits for proper sector to rotate under head READ/WRITE — disk head scans the sector for read or write

Magnetic Disks n FLOPPY DISKS n n n 5. 25 and 3. 5 inch diskettes CAV 1. 44 – 2. 88 MBytes capacity access: drive speeds – 600 r. p. m. inexpensive, archival uses for small amounts of data offline storage n HARD DISKS n n n 3. 5 inch has approx 1030 K tracks per side ZCAV multiple disk, sides (cylinders) high capacity access: drive speeds – 5, 400; 7, 200 r. p. m. and higher on-line storage

Disk vs. File Organization n n n n data is stored in blocks occupy sectors on tracks files have names files are indefinite in size files may be updated (in part or whole) directory entries record file data file allocation table keeps track of file pieces

CD-ROM n n n n based on CDDA technology CLV geometry density: 16, 000 tpi up to 650 MBytes nonerasable, nonwriteable storage discs are mastered, pressed (mass production) multispeeds drives common

CD–R n n discs are “burnt” one at a time high intensity laser beam used for recording pregrooved tracks low intensity beam for reading attributes similar to CDROM

CD-RW n n CD-Re. Writable-writable, erasable disc optical phase-change recording Erased, written up to 1, 000 times UDF (Universal Disk Format) n n variable-length packets fixed-length packets

DVD n n n Digital Versatile Disc second generation CD-ROM higher capacity: n n n higher data density multiple sides multiple layers