CSC204_ch01-1
CSC 204: Information Technology and Networking
PART
I
Chapters
1. System Unit
2. Specialized Application Software
3. System Software
Chapter 1
System Unit
Ralph El Khoury, Wajdi Abboud
Outline
•
•
•
•
•
•
•
•
•
Introduction
System Unit
System board or motherboard
Microprocessor
Memory
System clock
Bus line
Ports
Expansion slots and cards
Information Technology and Networking
CSC204_PartI-ch01-2
Introduction
• Computer:
– A set of electronic circuits that allows to
manipulate binary data
• Three main categories of a computer:
– Compute
– Manage data
– Communicate (User – PC, PC – PC)
• Display data to the screen or with a printer
• Write with a keyboard
• Exchange information in the Internet
Information Technology and Networking
CSC204_PartI-ch01-3
Introduction
• The data and the instructions are represented with
electronic devices
• Computers understand only digital signals
– in opposite to analog signals
• Binary system
– Each 0 and 1 is called bit
– A bit is the simple unit used by the computer
– A byte is the useful data unit
• 8 bits = 1 byte
• 1Kb = 1000 bits
• 1KB = 1000 bytes = 8000 bits
Information Technology and Networking
CSC204_PartI-ch01-4
Introduction
• Computer character coding :
– Gives a binary representation to characters (including
letters, digits, symbols, etc…)
– Characters are represented with a series of 0 and 1
• using 8 or 16 bits
• E.g.: character A is represented by 01000001 in ASCII code
• There are 3 types of character coding
– ASCII - American Standard Code for Information
Interchange
– EBCDIC - Extended Binary Coded Decimal Interchange
Code
– Unicode – used to encode a large number of characters
from different international languages.
Information Technology and Networking
CSC204_PartI-ch01-5
System unit
• Also known as the
chassis,
– resides inside the box of
the computer
• Houses most of the
electronic components
that make up a computer
system
– E.g., motherboard,
microprocessor, memory
Information Technology and Networking
CSC204_PartI-ch01-6
System board or motherboard
•
It is the communications medium for the entire
computer system
–
•
•
because every component of the system unit connects to
the system board.
It is a large flat circuit board covered with a variety
of different electronic components.
It is composed of:
1.
2.
3.
4.
sockets
chips
slots
connecting lines
Information Technology and Networking
CSC204_PartI-ch01-7
System board or motherboard
1. Sockets
– provide a connection point for small specialized electronic
parts called chips.
2. Chips
– A chip or integrated circuit
3. Slots
– provide a connection point for specialized cards or circuit
boards.
– These cards provide expansion capability for a computer
system.
4. Connecting lines called bus lines
– provide pathways that support communication among the
various electronic components
Information Technology and Networking
CSC204_PartI-ch01-8
Microprocessor
• The central processing
unit (CPU) or processor
is contained on a single
chip called the
microprocessor.
– Can contain a million of
transistors
• The microprocessor is
the "brains" of the
computer system.
Information Technology and Networking
Microprocessor mounted with a fan
CSC204_PartI-ch01-9
Microprocessor
•
It is composed with 3 components:
1.
2.
3.
The control unit (CU): coordinate the computer activity
The arithmetic/logic unit (ALU): performs two types of operations:
arithmetic and logical
Registers: temporary storage of information
–
–
General-purpose registers
Special-purpose registers: Program Counter (PC), Instruction register (IR), …
Information Technology and Networking
CSC204_PartI-ch01-10
Microprocessor
Registers
• Small memory with size around 32 to 128 bits each,
located inside CPU
– We can find up to a hundred of registers
• Store temporary data while executing instructions
– Execution becomes more efficient
• Several types of CPU registers are used:
– General Purpose Registers (GPR)
– Special-purpose registers
•
•
•
•
Program Counter (PC)
Instruction Register (IR)
Accumulator (A)
Flag Register (FR)
Information Technology and Networking
CSC204_PartI-ch01-11
Microprocessor
Registers
1. General Purpose Registers
– used for various tasks.
•
E.g., store intermediate results of the ALU operations.
2. Program Counter register
– contains the address of the next instruction to be executed
3. Instruction register
– used to hold the instruction being executed
4. Accumulator
– Results of arithmetic and logical operations always go to the
accumulator.
5. Flag register
– stores the status of the last operation carried out by the ALU.
•
states such as: overflow, division by zero, final result is a zero, positive or
negative result, results of comparisons
Information Technology and Networking
CSC204_PartI-ch01-12
Microprocessor
Arithmetic/Logic Unit (ALU)
• The ALU performs two types of operations:
• Arithmetic operations
– Addition, subtraction, multiplication, division
• Logic operations
– Using the operators: AND, OR, NOT, …
Information Technology and Networking
CSC204_PartI-ch01-13
Microprocessor
Control Unit (CU)
• The CU coordinates the computer activity
• Dictate other units of the computer how to run the
program instructions (command others what to do)
• Directs the flow of bits
– Between main memory and ALU
– Between the CPU and IO devices
• Synchronizes the execution of instructions to
the rhythm of a clock
Information Technology and Networking
CSC204_PartI-ch01-14
CPU Speed
•
CPU speed depends mainly on 4 characteristics
1. Word size
•
•
A word is the number of bits (such as 16, 32, or 64) that can be
manipulated at one time by the CPU.
A CPU with a 64 bits is more powerful than another with a 32 bits
2. Execution frequency
•
•
•
•
Mainly depends on the clock speed
Expressed in GHz (109 Hz), a billion of impulsion cycle per
second
An instruction executes in one or more cycles, then
The average of the instructions executed per second characterize
the speed of the CPU
Information Technology and Networking
CSC204_PartI-ch01-15
CPU Speed
3. Multi-core processor
–
–
–
–
–
Put in the same chip two or more processors
Can double the performance without changing
the clock frequency
Processors executes in parallel (in the same time)
Need to adapt system and application software
E.g. Core 2 Duo, …
4. Cache memory
–
A large cache memory can speed up the CPU
execution
Information Technology and Networking
CSC204_PartI-ch01-16
Memory
RAM (random-access memory )
• Hold the program (sequence of instructions) and data that
the CPU is presently processing.
• RAM is temporary or volatile storage
– because everything in most types of RAM is lost as soon as the
microcomputer is turned off.
• Sufficient RAM size is needed for executing large and
many programs
• DRAM and SDRAM are dynamic memories
– allows less time for retrieving data
• Virtual memory
– is a space used on a secondary storage device by the operating
system when there isn't enough RAM to process all applications.
Information Technology and Networking
CSC204_PartI-ch01-17
Memory
• ROM (read-only memory)
– Have programs built into them at the factory.
• E.g., BIOS (Basic Input Output System)
– ROM chips are not volatile and cannot be changed by the user
• CMOS (complementary metal-oxide semiconductor)
– Small memory that contains essential information that is required
every time the computer system is turned on.
– E.g., the current date and time, type of keyboard, mouse, monitor, and
disk drives.
Information Technology and Networking
CSC204_PartI-ch01-18
Memory
• Cache memory
– Fast to access memory with a capacity around some
Megabytes
– Its location is near the CPU, nearer than the main memory
(RAM)
• Reduce the waiting times for executing instructions
– Store temporary the information that will be soon executed by
the CPU
• Store frequently used information
• Ameliorate the performance of the applications
• Flash memory
– Not volatile, high cost, easy for data transportation, e.g key usb
Information Technology and Networking
CSC204_PartI-ch01-19
Memory characteristics
• Capacity in number of bytes
– E.g., 1GB (i.e. 1024MB), 256MB, 512MB
• Access time
– time interval between the request for reading/writing and
the availability of data
• Cycle time
– Minimum interval time between two successive access
• Rate
– Maximal number of information that can be read or written
in the memory
• Volatility
– aptitude of the memory for conserving data when the
computer is turned off
Information Technology and Networking
CSC204_PartI-ch01-20
The System Clock
• Control the speed operation of the computer
• Located on a small specialized chip
• Indicates the speed of processing (operations) of a
computer system
• Measured in gigahertz (GHz) or billion cycles per
second
• There are two clocks
– One speed operations on the bus
– The other, operations inside the CPU
Information Technology and Networking
CSC204_PartI-ch01-21
Buses
• Buses connect
– the parts of the CPU to each other.
– the CPU to various other components on the system board.
• Transport data, instructions and addresses
• Bus size
– the number of bits that can traverse in the same time on the
bus
– A bus with 64 bits has a capacity larger than one with 16
bits, then the speed of the computer is higher
Information Technology and Networking
CSC204_PartI-ch01-22
Buses
• There are two types of buses
– System bus: connects the CPU to memory on the system
board.
– Expansion bus: connects the CPU to other components on
the system board.
• There are many types of expansion bus
1. ISA (Industry Standard Architecture)
2. PCI (Peripheral Component Interconnect)
3. AGP (Accelerated Graphics Port)
4. USB (Universal Serial Bus)
5. HPSB (High-performance Serial Bus, FireWire buses)
Information Technology and Networking
CSC204_PartI-ch01-23
Buses
1. ISA (Industry Standard Architecture) bus
– An old standard that connects expansion cards on the
motherboard
– Use to connect low peripherals
• E.g., modem or sound card
• Bus size: 8 or 16 bits
2. PCI (Peripheral Component Interconnect) bus
– developed to meet the video demands of graphical user
interfaces.
– Bus size: 32 or 64 bits. Speed: 130 – 528MB/s
– Standard that connects expansion cards on the motherboard
– Used for the expansion cards: sound, graphic, network
Information Technology and Networking
CSC204_PartI-ch01-24
Buses
3. AGP (Accelerated graphics port):
–
–
Dedicated to the acceleration of graphics
performance.
Used for the transfer of video data.
4. USB (Universal serial bus)
–
support several external devices without using
expansion cards.
5. FireWire buses operate much like USB
buses.
Information Technology and Networking
CSC204_PartI-ch01-25
Ports
• A port is a socket for external devices to
connect to the system unit
• We distinguish many types of ports
–
–
–
–
–
–
–
Parallel port
Serial port
USB port
Firewire port
PS/2 port
VGA port
RJ45 port
Information Technology and Networking
CSC204_PartI-ch01-26
Ports
• Parallel port: parallel bits transfer (at the
same time)
• Serial port: transfer bits one after the other
• USB port
– replacing serial and parallel ports
– fast data transfer
– allows the connection of parallel devices at the
same time
– allows connection/disconnection of device using
the plug and play standard
Information Technology and Networking
CSC204_PartI-ch01-27
Ports
• FireWire port
– faster than USB port, designed for video transfer
• PS/2 port
– connects the mouse and the keyboard
• VGA port
– connects the graphical card to the screen
• RJ45 port
– connects a network cable to the network card
Information Technology and Networking
CSC204_PartI-ch01-28
Expansion slots and cards
• Expansion cards plug into slots
located on the system board.
• Ports on the cards allow cables
to be connected from the
expansion cards to devices
outside the system unit.
• Some of the more common
devices are
– video cards, sound cards, modem
cards, network interface cards, and
TV Tuner cards.
Information Technology and Networking
CSC204_PartI-ch01-29
References
• Book
– Computing essentials 2008, O'leary, O'leary
• Web Sites
–
–
–
–
–
–
http://www.c2imes.org
http://www.commentcamarche.net/
http://www.vulgarisation-informatique.com/
http://www.ybet.be/
Encyclopedia: Wikipedia
Notes : Architecture des ordinateurs, T. Dumartin
Information Technology and Networking
CSC204_PartI-ch01-30