Storing Data On Your Computer

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

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

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

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

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

6. Memory Hierarchy I

7. Memory Hierarchy II

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

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

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

11. DASD Media • 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

12. Direct Access • 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

13. FLOPPY DISKS 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 HARD DISKS 3.5 inch has approx 10-30K 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 Magnetic Disks

14. Disk vs. File Organization • data is stored in blocks • blocks occupy sectors • 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

15. CD-ROM • 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

16. CD–R • discs are “burnt” one at a time • high intensity laser beam used for recording pregrooved tracks • low intensity beam for reading • attributes similar to CD-ROM

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

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