• Computer Architecture
Full Chapter
• By Fazal Rehman (Shamil)
ITC : By Fazal Rehman(Shamil)
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Objectives Overview
Differentiate among various
styles of system units on
desktop computers,
notebook computers, and
mobile devices
Describe the control unit
and arithmetic logic unit
components of a processor,
and explain the four steps in
a machine cycle
Define a bit and describe
how a series of bits
represents data
Differentiate among the
various types of memory
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Objectives Overview
Describe the purpose
and types of expansion
slots and adapter cards
Differentiate between a
port and a connector,
and explain the
differences among a USB
port and other ports
Describe the types of
buses in a computer
Understand how to clean
a system unit on a
computer or mobile
device
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The System Unit
• The system unit is a case that contains electronic components of the
computer used to process data
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The System Unit
• The inside of the system unit on a desktop personal
computer includes:
Drive bay(s)
Power supply
Sound card
Video card
Processor
Memory
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The System Unit
• The motherboard is the main circuit board of the system
unit
– A computer chip contains integrated circuits
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Processor
• The processor, also called the central processing unit (CPU),
interprets and carries out the basic instructions that operate
a computer
– Contain a control unit and an arithmetic logic unit (ALU)
Multi-core
processor
Dual-core
processor
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Quad-core
processor
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multi-core processor
• A multi-core processor is a single computing component
with two or more independent actual CPU’s.
Model
Core i3
Core i5
Core i7
Number of
cores
2
4
4
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• Quad Cores has 4 cores
• Core 2 due has 2 cores
• Dual core has 2 cores
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Processor
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Processor
• The control unit is the component of the processor that
directs and coordinates most of the operations in the
computer
• The arithmetic logic unit (ALU) performs arithmetic,
comparison, and other operations
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Processor
• For every instruction, a processor repeats a set of four basic
operations, which comprise a machine cycle
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Processor
The system clock controls the
timing of all computer operations
•The pace of the system clock is called the
clock speed, and is measured in gigahertz
(GHz)
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Data Representation
Most computers are digital
Digital signals are in one of two states: on or off
• Most computers are digital
• The binary system uses two unique digits (0 and 1)
• Bits and bytes
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Data Representation
A computer circuit represents the 0 or
the 1 electronically by the presence or
absence of an electrical charge
Eight bits grouped together as a unit
are called a byte. A byte represents
a single character in the computer
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Data Representation
• ASCII (American Standard
Code for Information
Interchange) is the most
widely used coding scheme
to represent data
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Data Representation
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Cache
• The speed of CPU is extremely high compared to the
access time of main memory.
• Therefore the performance of CPU decreases due to the
slow speed of main memory.
SO
• CPU required its own memory.
• The solution to this problem are Cache memory and
registers.
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Cache
• Cache Memory is a small memory chip is attached
between CPU and Main memory whose access time is
very close to the processing speed of CPU.
• CACHE memories are accessed much faster than
conventional RAM. It is used to store programs or data
currently being executed or temporary data
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Register
• Register is a small amount of memory available as part
of a digital processor, such as a CPU. Such registers are
(typically) addressed by mechanisms other than main
memory and can be accessed faster.
• Processor registers are normally at the top of
the memory hierarchy, and provide the fastest way to
access data.
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Examples of registers
• PCR-Program counter Register:
• Controls the sequence in which instructions are fetched
from memory.
• It stores the address of next instruction to be fetched for
execution.
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Examples of registers
• MAR-Memory Address Register:
Holds the memory addresses of data and instructions.
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Examples of registers
IR- Instruction Register:
• Once an instruction is fetched from main memory, it is
stored in the instruction register.
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Examples of registers
• MBR- Memory Buffer Register:
• Holds the contents of data or instructions read from, or
written in memory.
• Also called data register.
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Examples of registers
• Accumulator Register:
• Located inside ALU.
• Used during arithmetic and logical operations
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Memory
• Memory consists of electronic components that store
instructions waiting to be executed by the processor, data
needed by those instructions, and the results of processing
the data
• Stores three basic categories of items:
The operating
system and other
system software
Application
programs
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Data being
processed and the
resulting
information
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Memory
• Each location in memory has an address
• Memory size is measured in kilobytes (KB or K), megabytes
(MB), gigabytes (GB), or terabytes (TB)
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Memory
• The system unit contains two types of memory:
Volatile memory
Nonvolatile memory
Loses its contents when
power is turned off
Does not lose contents
when power is removed
Example includes RAM
Examples include ROM,
flash memory, and CMOS
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Memory
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Memory
• Three basic types of RAM chips exist:
Dynamic RAM
(DRAM)
Static RAM (SRAM)
Magnetoresistive
RAM (MRAM)
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SRAM
It is faster than DRAM.
It is more expensive as compared to DRAM.
It does not need to be power – refreshed.
It utilizes less power.
It holds data indefinitely as long as the computer is
turned on.
• It is more complex and less compact.
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DRAM
It is slower than SRAM.
It is less expensive.
It has to be refreshed after each read operation.
It utilizes more power.
It holds data dynamically not indefinitely.
It is less complex and more compact.
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• MRAM (Magneto resistive Random Access Memory)
• MRAM stands for Magneto resistive Random Access Memory. It
stores data using magnetic charges instead of electrical charges.
MRAM uses far less power than other RAM technologies so it is
ideal for portable devices. It also has greater storage capacity. It
has faster access time than RAM. It retains its contents when the
power is removed from computer.
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Memory
• RAM chips usually reside on a memory module and are
inserted into memory slots
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Memory
• The amount of RAM necessary in a computer often depends
on the types of software you plan to use
• Memory cache speeds the processes of the computer
because it stores frequently used instructions and data
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Memory
Read-only memory (ROM) refers to memory
chips storing permanent data and
instructions
• ROM is a Firmware
• Firmware is a combination of both hardware and
software.
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Read Only Memory (ROM) Types
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Basic ROM types:
ROM - Read Only Memory
PROM - Programmable Read Only Memory
EPROM - Erasable Programmable Read Only Memory.
– Data can be erased by special devices.
• EEPROM - Electrically Erasable Programmable Read Only Memory
– Data can be erased by electrical pulses
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Memory
• Flash memory can be erased
electronically and rewritten
– CMOS technology provides
high speeds and consumes
little power
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Memory
• Access time is the amount of time it takes the processor to
read from memory
– Measured in nanoseconds
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Expansion Slots and Adapter Cards
• An expansion slot is a socket on
the motherboard that can hold an
adapter card
• An adapter card enhances
functions of a component of the
system unit and/or provides
connections to peripherals
– Sound card and video card
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Expansion Slots and Adapter Cards
• Removable flash memory includes:
– Memory cards, USB flash drives, and PC Cards/ExpressCard
modules
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Ports and Connectors
A port is the point at which a peripheral attaches to or
communicates with a system unit (sometimes referred
to as a jack)
A connector joins a cable to a port
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Ports and Connectors
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Ports and Connectors
• On a notebook computer, the ports are on the back, front,
and/or sides
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Ports and Connectors
• A USB port can connect up to 127 different peripherals
together with a single connector
– You can attach multiple peripherals using a single USB port with a
USB hub
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Ports and Connectors
• A port replicator is an external
device that provides connections
to peripherals through ports built
into the device
• A docking station is an external
device that attaches to a mobile
computer or device
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Buses
• A bus allows the various devices
both inside and attached to the
system unit to communicate
with each other
– Data bus
– Address bus
• A computer can have these
basic types of buses:
– System bus
– Backside bus
– Expansion bus
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Bays
• A bay is an opening inside the
system unit in which you can
install additional equipment
– A drive bay typically holds disk
drives
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Power Supply
The power supply converts the wall outlet
AC power into DC power
Some external peripherals have an AC
adapter, which is an external power supply
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Putting It All Together
Home
Intel Core 2 Duo or Intel
Celeron Dual Core or AMD
Sempron
Small Office/
Home Office
Intel Core 2 Quad or Intel Core
2 Extreme or AMD Athlon FX
or AMD Athlon X2 Dual-Code
Mobile
Intel Core 2 Extreme or AMD
Turion X2
Minimum RAM: 2 GB
Minimum RAM: 2 GB
Minimum RAM: 4 GB
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Putting It All Together
Power
Enterprise
Intel Itanium 2 or AMD
Quad Core Opteron or Intel
Quad Core Xeon or Sun
UltraSPARC T2
Intel Core 2 Quad or Intel
Core 2 Extreme or AMD
Athlon FX or AMD Athlon X2
Dual-Core
Minimum RAM: 8 GB
Minimum RAM: 4 GB
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Summary
Components of the
system unit
How memory stores
data, instructions, and
information
Sequence of
operations that occur
when a computer
executes an instruction
Comparison of various
personal computer
processors on the
market today
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