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...