pc peripherals
DESCRIPTION
Introduction to PCTRANSCRIPT
Chapter 10 Computer Peripherals
10-1
Peripherals
Devices that are separate from the basic computer Not the CPU, memory, power supply
Classified as input, output, and storage Connect via
Ports parallel, USB, serial
Interface to systems bus SCSI, IDE, PCMCIA
Chapter 10 Computer Peripherals
10-2
Storage Devices
Primary memory Expanded storage Secondary storage
Data and programs must be copied to primary memory for CPU access
Permanence of data Direct access storage devices (DASDs) Online storage Offline storage – loaded when needed
Chapter 10 Computer Peripherals
10-3
Speed
Measured by access time and data transfer rate
Access time: average time it takes a computer to locate data and read it millisecond = one-thousandth of a second
Data transfer rate: amount of data that moves per second
Chapter 10 Computer Peripherals
10-4
Hierarchy of Storage
Device Throughput Rate
CPU Registers
Cache Memory (SRAM) 15 to 30 nanoseconds
Conventional Memory (DRAM) 50 to 100 nanoseconds
Expanded Storage (RAM) 75 to 500 nanoseconds
Hard Disk Drive 10 to 50 milliseconds 600 to 6,000 KB/sec
Floppy Disk 95 milliseconds 100 to 200 KB/sec
CD-ROM 100 to 600 milliseconds 500 to 4,000 KB/sec
Tape .5 and up seconds 2,000 KB/sec (cartridge)
Typical Access Times
Chapter 10 Computer Peripherals
10-5
Secondary Storage Devices
Hard drives, floppy drives CD-ROM and DVD-ROM drives CD-R, CD-RW, DVD-RAM, DVD-RW Tape drives Network drives Direct access vs. Sequential access Rotation vs. Linear
Chapter 10 Computer Peripherals
10-6
Magnetic Disks Track – circle Cylinder – same track on all platters Block – small arc of a track Sector – pie-shaped part of a platter Head – reads data off the disk
Head crash Parked heads Number of bits on each track is the same! Denser towards the
center. CAV – constant angular velocity
Spins the same speed for every track Hard drives – 3600 rpm – 7200 rpm Floppy drives – 360 rpm
Chapter 10 Computer Peripherals
10-7
A Hard Disk Layout
Chapter 10 Computer Peripherals
10-8
Locating a Block of Data Average seek time: time
required to move from one track to another
Latency: time required for disk to rotate to beginning of correct sector
Transfer time: time required to transfer a block of data to the disk controller buffer
Chapter 10 Computer Peripherals
10-9
Disk Access Times
Avg. Seek time average time to move from one track to another
Avg. Latency time average time to rotate to the beginning of the
sector Avg. Latency time = ½ * 1/rotational speed
Transfer time 1/(# of sectors * rotational speed)
Total Time to access a disk block Avg. seek time + avg. latency time + avg. transfer time
Chapter 10 Computer Peripherals
10-10
Magnetic Disks
Data Block Format Interblock gap Header Data Formatting disk
Disk Interleaving Disk Arrays
RAID – mirrored, striped Majority logic fault-tolerant computers
Disk Interleaving
Chapter 10 Computer Peripherals
10-11
Disk Block Formats
Single Data Block
Header for Windows disk
Chapter 10 Computer Peripherals
10-12
Alternate Disk Technologies Removable hard drives
Disk pack – disk platters are stored in a plastic case that is removable
Another version includes the disk head and arm assembly in the case
Fixed-head disk drives One head per track Eliminates the seek time
Bernoulli Disk Drives Hybrid approach that incorporates both floppy and hard disk
technology Zip drives
Chapter 10 Computer Peripherals
10-13
Magnetic Tape
Offline storage Archival purposes Disaster recovery Tape Cartridges
20 – 144 tracks (side by side) Read serially (tape backs up) QIC – quarter inch cartridge (larger size) DAT – digital audio tape (small size) Size typically includes (2:1 compression)
Chapter 10 Computer Peripherals
10-14
Optical Storage Reflected light off a mirrored or pitted surface CD-ROM
Spiral 3 miles long, containing 15 billion bits! CLV – all blocks are same physical length Block – 2352 bytes
2k of data (2048 bytes) 16 bytes for header (12 start, 4 id) 288 bytes for advanced error control
DVD-ROM 4.7G per layer Max 2 layers per side, 2 sides = 17G
Chapter 10 Computer Peripherals
10-15
Optical Storage
Laser strikes land: light reflected into detector Laser strikes a pit: light scattered
Chapter 10 Computer Peripherals
10-16
Layout: CD-ROM vs. Standard Disk
CD-ROM Hard Disk
Chapter 10 Computer Peripherals
10-17
CD-ROMsSeek Time
(milliseconds)
Single-Speed 600 150K per second
2X 320 300K per second
3X 250 450K per second
4X 135-180 600K per second
6X 135-180 900K per second
8X 135-180 1.2 MBps
10X 135-180 1.6 MBps
12X 100-150 1.8 MBps
16X 100-150 2.4 MBps (maximum)
24X 100-150 3.6 Mbps (maximum)
32X 100-150 4.8 Mbps (maximum)
General Speed Data Transfer Rate
Chapter 10 Computer Peripherals
10-18
Types of Optical Storage WORM Disks
Write-once-read-many times Medium can be altered by using a medium-powered laser to
blister the surface Data stored in concentric tracks, sectored like a magnetic
disk CAV
Medium-powered laser blister technology also used for CD-R, DVD-R, DVD-ROM CD-RW, DVD-RW, DVD-RAM, DVD+RAM
Magneto-Optical Disks
Chapter 10 Computer Peripherals
10-19
Displays Pixel – picture element Size: diagonal length of screen Resolution (pixels on screen)
VGA: 480 x 640 SVGA: 600 x 800 768 x 1024 1280 x 1024
Picture size calculation Resolution * bits required to represent number of
colors in picture Example: 16 color image, 100 pixels by 50 pixels
4 bits (16 colors) * 100 * 50 = 20,000 bits
Chapter 10 Computer Peripherals
10-20
Display Screen Screen size: measured
diagonally Resolution: minimum
identifiable pixel size Aspect ratio: x pixels to
y pixels 4:3 on most PCs 16:9 on high definition
displays
Chapter 10 Computer Peripherals
10-21
Color and Displays
Pixel color is determined by intensity of 3 colors – Red Green Blue or RGB
4 bits per color 16 x 16 x 16 = 4096 colors
24 bit color (True Color) 16.7 million colors
Video memory requirements are significant!
Chapter 10 Computer Peripherals
10-22
CRT’s and Text Monitors CRTs (similar to TVs)
3 stripes of phosphors for each color 3 separate electron guns for each color Strength of beam brightness of color Raster scan
30x per second Interlaced vs. non-interlaced (progressive scan)
Text monitors 24 lines x 80 chars A character is the smallest unit on a screen Very little memory required Fast for remote transmissions
Chapter 10 Computer Peripherals
10-23
Interlaced vs Noninterlaced
Chapter 10 Computer Peripherals
10-24
Diagram of Raster Screen Generation Process
Chapter 10 Computer Peripherals
10-25
Display Example
Chapter 10 Computer Peripherals
10-26
LCD – Liquid Crystal Display
Fluorescent light panel 3 color cells per pixel Operation
1st filter polarizes light in a specific direction Electric charge rotates molecules in liquid crystal
cells proportional to the strength of colors Color filters only let through red, green, and blue
light Final filter lets through the brightness of light
proportional to the polarization twist
Chapter 10 Computer Peripherals
10-27
LCD Operation
Chapter 10 Computer Peripherals
10-28
LCDs (continued)
Active matrix One transistor per cell More expensive Brighter picture
Passive matrix One transistor per row or column Each cell is lit in succession Display is dimmer since pixels are lit less
frequently
Chapter 10 Computer Peripherals
10-29
Printers Dots vs. pixels
300-2400 dpi vs. 70-100 pixels per inch Dots are on or off, pixels have intensities
Types Typewriter / Daisy wheels – obsolete Dot matrix – usually 24 pins, impact printing Inkjet – squirts heated droplets of ink Laserjet Thermal wax transfer Dye Sublimation
Chapter 10 Computer Peripherals
10-30
Creating a Gray Scale
Chapter 10 Computer Peripherals
10-31
Laser Printer Operation
1. Dots of laser light are beamed onto a drum2. Drum becomes electrically charged3. Drum passes through toner which then sticks to
the electrically charged places4. Electrically charged paper is fed toward the drum5. Toner is transferred from the drum to the paper6. The fusing system heats and melts the toner
onto the paper7. A corona wire resets the electrical charge on the
drum
Chapter 10 Computer Peripherals
10-32
Laser Printer Operation
Chapter 10 Computer Peripherals
10-33
Laser Printer Operation
Chapter 10 Computer Peripherals
10-34
Other Computer Peripherals
Scanners Flatbed, sheet-fed, hand-held Light is reflected off the sheet of paper
User Input Devices Keyboard, mouse, light pens, graphics
tablets Communication Devices
Telephone modems Network devices