information systems hw. definition a computer consists of: central processing unit (cpu) primary...
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Information Systems HW
Definition
A computer consists of: Central Processing Unit (CPU) Primary storage Secondary storage Input devices Output devices Communications devices
Definitions...
A chip contains millions of microminiature electronic circuit components.
A micro processor (processor on a chip) is the miniatuarized circuitry of a computer processor.
Central Processing Unit
CPU follows the instructions of the SW to manipulate data into information.
CPU consists of two parts: ALU (arithmetic/logic unit) CU (control unit)
Arithmetic / Logic Unit ALU performs the principal logical and
arithmetic operations (+, -, *, /, determine whether a no. is positive-negative-zero)
ALU can perform logical operations on characters and numbers (AND, OR, exclusive OR)
Control Unit
CU coordinates and controls the other parts of the computer system. Reads a stored program, one instruction at a time, and directs other components of the system to perform the tasks required by the program.
Main Memory Stores the part of the program
(instructions) that is being executed
Holds data that are being used by the program
Holds processed data waiting to be sent to an output device or secondary-storage device.
Main Memory Also called as memory, primary
memory, internal memory or RAM Data and programs are placed in
primary storage before processing Short-term storage Volatile
Factors effecting the speed Word length (16 bit - 32 bit) Cycle speed (MHz - megahertz) Data bus width Microprocessors can be made
faster by RISC
System Unit System unit contains the electrical and
HW components that make the computer work.
Peripheral devices are the HW that is outside the CPU.
Connectors connect mainboard to HDD, FDD and CD-ROM.
Some peripherals are connected by expansion (adapter or interface) cards
Primary Storage Stores all parts of a program that
will be executed Operating system programs Data used by the program
Secondary Storage Non-volatile storage of data
outside the CPU and primary storage. Hard disk - 20 GB - 15 msec. Diskette - 2.8 MB - 200 msec. Optical Disk - 660 MB - 200-500
msec. Magnetic Tape - 40 MB - 1-2 sec.
Magnetic Tape Inexpensive Usually used for backup storage Sequential Relatively slow
Magnetic Disk It is a must random access more expensive than tape faster than tape
Floppy Disk Removable Erasable Sector is a data is storage method
dividing disk into pie-shaped pieces (typically 512K)
Each sector is assigned a unique number Data is stored on tracks Magnetic disk made of thin polyester film
with magnetic coating
Hard Disk Read/write heads fly over the spinning disks Data access speed is determined by access
arm and spinning speed Heads move horizontally to any of 200
cylinders randomly Cylinders represent circular tracks on the
same vertical line Rotates about 3500 rpm Iron oxide coating Usually not removable
Optical Disk Data is recorded and read by laser beams Also called compact disks or laser optical
disks Content cannot easily be erased and
written over Access speed is slower than the magnetic
disks Long lifetime Plastic coating
CD-ROM Compact Disk - Read Only Memory Laser projects a beam of light reflects back to the detector Light pulses are translated into
small electric voltages They generate 0s and 1s
WORM / CD-R Write once/read many optical disks Alternative to microfilm archives CD-R : Compact disk - recordable Photo CD
Rewritable magneto-optical disks Disk surface can change magnetic polarity
only when heated. Coated by magnetic film. High-powered laser beam heats to record Erasable Data can be read by projecting a lower-
powered laser beam and reading the reflected light
Can be written nearly a million times Access speed is lower than magnetic disks
DVD Digital Convergence Disk - A new
generation of high density CD-ROM disk
Single-sided / single layer / 4.7 GB Single-sided / dual layer / 8.5 GB
Flash Memory Cards Used primarily in notebook Credit-card-sized inserted into slots Non-volatile Size is about 100 MB Can be used to simulate main memory
as well as to supplement hard disk drives
Other storage types CD-ROM Jukeboxes : 100 CD-ROMs
can be accessed at the same time using a network connection
Video Servers : deliver interactive video or movies through cable or other connections
Online databases : can be retrieved from Internet. Security is a problem.
RAM Chips Memory that temporarily holds data and
instructions that will be needed shortly by the CPU. Single Inline Memory Module (SIMM) Dual Inline Memory Module (DIMM) DRAM - Dynamic RAM SRAM - Static RAM EDO RAM - Extended Data Out RAM
Comparing bandwidth SDRAM 100MHz x 64bit = 800 MB/sec SDRAM 133MHz x 64bit = 1064 MB/sec DDRAM 2 x (100MHz x 64bit) = 1600
MB/sec DDRAM 2 x (133MHz x 64bit) = 2128
MB/sec RDRAM 800MHz x 16bit = 1600 MB/sec
RDRAM Rambus RAM developed from DRAM data is read in packets with very
high clock speed Modules are only 16 bits 800 MHz, GigaHertz will follow All RAM slots must be full even not
used
DDRAM DDR - Double Data Rate : a
technology that transmits data on both sides of a tact signal
All major vendors except Intel supports DDR-SDRAM
DDR-SDRAM will be cheaper than Rambus RAM yet giving the same performance.
Multibank DRAM (MDRAM) Specifically designed to use in
graphic cards breaks up the memory to 32 KB
banks each bank can be addressed
independently
Synchronous Graphics RAM SGRAM greatly increased the
transfer speed compared to DRAM. Incorporates specific performance
enhancing features designed to work with video cards.
Greatly improves overall video processing speed.
VRAM - WRAM VRAM - Video Memory - to store
display images for the monitor. Determines the speed and number of colours available.
WRAM - Window RAM is a modification of VRAM with improved performance and reduced cost. Designed specifically for use in graphic cards.
Comparison chartTech. Access port Bandwidth Rel. cost Target
marketStd. DRAM Single Low Low Low
EDO RAM Single Low Low Low
VRAM Dual High High Medium tohigh
WRAM Dual High High High
SGRAM Single Very high Moderate Medium
MDRAM Single Very high High Medium tohigh
ROM Chips Read only memory cannot be
written or erased without special equipment
BIOS - Basic Input Output System
Cache Memory Used for high speed storage of
frequently used instructions and data Can be located on the microprocessor
chip or elsewhere on the main board (Pentium II - at least 512K) L1 (8-64KB) caches L2, System RAM, HDD L2 (64KB-2MB) caches System RAM, HDD System RAM caches HDD
Expansion Slots and Board Sockets on the main board to plug
expansion cards Used to provide more memory or
control peripheral devices. Expanded memory: RAM Display or graphics adapter cards Controller cards (HDD, FDD, etc) Others (modem, network, sound, etc)
Input Devices Keyboard Pointing Devices : control the
position of cursor or pointer on the screen (mouse, joystick, trackball, touchpad, pen-based systems, touch screen)
Input Devices Source Data-Entry Devices create
machine-readable data on magnetic media or paper or feed it directly into the computer. (Scanners, barcode, fax, magnetic stripe card, smart card, sensors, audio-input devices, video input devices, electronic cameras, human-biology input devices)
Scanners use laser beams and reflected light to translate images into digital form.
Output Devices CRT terminals, printers, plotters,
speakers (voice output devices) Dot-matrix printer Laser printer Inkjet printers Thermal printers Multi function devices combine printing,
scanning, copying and faxing capabilities in one device.
Virtual Reality Devices Computer-generated artifical reality
that project a person into a sensation of three-dimensional space. VR equipment : headgear, glove, suit,
etc. Future : 3-D TVs, 3-D scanners,
biometric devices, brain-wave devices...