Storage Devices

Chapter 4

Memory Cache

 Speeds up computer by storing data the computer has recently used  Internal Cache: On CPU chip (L1 or primary cache  External Cache: On the system board and consists of Static RAM (SRAM chips)  Sometimes built into chip  RAM – slower main memory  Each time the computer requests data from RAM, the computer places a copy of the data in memory cache  Constantly contains the most recently used data

BUS

 Electronic pathway that carries information between devices in a computer  Bus Width (think lanes of a highway)  8 bits is one character  Bus Speed (think speed limit)  Measured in MHz (millions of cycles per second)

Bus Types

   ISA (Industry Standard Architecture)    Slowest and oldest 16 bits; 8MHz (millions of cycles per second) Pentium, Pentium II PCI (Peripheral Component Interconnect)  32 or 64 bits    66 MHz Support Plug and Play Pentium II, III, 4 AGP (Accelerated Graphics Port)  Between video card and main memory  32 bits; 66 MHz

Using a Hard Drive Correctly

 Virus protection  Backups  Defragmentation  Prevents files from being broken up for storage  Repairing a Disk  Disk Cleanup  Data compression  Only if disk is running out of space

Hard Drives

 Magnetically stores data on rotating disks called platters  Stores your operating system and programs  Document will not be lost when you turn off the computer  Capacity is measured in bytes  Speed is measured in revolutions per minute

File Systems

 File system determines how information is stored on a hard drive  FAT  FAT32  NTFS

Connection Types

 EIDE (Enhanced Integrated Drive Electronics) – Called IDE  Supports total of 4 devices (any drives)  Ultra Direct Memory Access (UDMA) is enhanced IDE  SCSI (Small Computer System Interface)  Called ‘scuzzy”  Supports 7 devices  Expensive

Relation of Cache & Hard Drives

 Disk cache speeds up the computer by storing the data the computer has most recently used  Constantly updated  Area of memory  Fast access  Then hard drive is searched

Floppy Drives and Drives

 Removable media  Can be write-protected  Can be damaged magnetically

CD-ROM

 ROM (Read-only memory) - can’t be changed  650 Mb of data  Equal to entire set of encyclopedias  400 Floppy disks  Music, games, software installs  Speed determines how fast a disk spins  Look for 24X  Speed of CD-ROM drive is the transfer rate  In Kb (e.g. 3600Kbs)

CD-R & CD-RW Drives

 CD-R (Compact Disc – Recordable)  Permanent store; not erasable  CD-RW  Can be erased and rewritten  Read / Write and Re-write speeds  Usually 74 minutes  Special software needed to record onto a disk  Referred to as burning a CD

DVD-ROM Drive

 DVD – Digital Versatile Disk  Generally cannot change the information stored on a disk  Similar to CD but stores more information  Speed determines transfer rate (6 X)  Capacity  1 side / 1 layer – 4.7 GB  1 side / 2 layer – 8.5 GB  2 sides / 1 layer – 9.4 GB  2 sides / 2 layers – 17 GB

Tape Drive

 Backup helps you copy files to tape cartridges  Tape drives come with backup programs  Schedule backups to run at night  Backup programs compress data together  Try to find a drive that can store the entire contents of your hard drive  Travan drives are the most common type of tape drives – 10 GB  DAT drives are faster than a Travan – 24GB

Tape Backups

 Full  Incremental

Removable Storage Devices

 Jazz Drive – 2 GB  Zip Drive – 250 MB  LS-120 Drive – 120 MB