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INSIDE THE COMPUTER:
CENTRAL PROCESSING UNIT (CPU)
AND INPUT/OUTPUT DEVICES
EXPANSION BOARDS : adding capabilities
Graphics adapter –
permit interfacing with video monitors
(VGA video graphics array and AGP
accelerated graphics port enable interfacing
of high-resolution monitors with the processor)
Sound card –
enables sound to be captured and stored on
disk; and enables sound to be played through
external speakers
Data/voice/fax modem – permits communication with remote
computers via a telephone-line link.
On top of the functions of a regular modem,
this one also enables you to make phone calls,
and allows your PC to mimic a fax machine.
IDE cable
Data
buses
A fleet of buses
ISA bus –
the oldest and the slowest
is being phased out of modern PCs
PCI local bus – enables expansion boards to be linked
directly to the system’s common bus
SCSI bus –
alternative to the expansion bus
up to 15 devices can be linked along a
single cable (daisy chained),
internal and external, with multiple SCSI
connectors
USB (universal serial bus) – permits up to 127 peripheral
devices to be connected to a single USB
port.
Eliminates the hassle of installing
expansion cards.
The Motherboard
Serial versus Parallel Ports
Serial port –
allows the serial transmission of data, one
bit at a time
eg. An external modem
Parallel port –
allows the parallel transmission of data
ie several bits simultaneously
eg printers, external magnetic disk units,
and other computers
SCSI port –
provides parallel interface to the SCSI bus
that enables faster data transmission than
serial and parallel ports
Intel 80826 microprocessor
von Neumann Architecture :
A memory containing both data and instructions. Also to
allow both data and instruction memory locations to be
read from, and written to, in any desired order.
A calculating unit capable of performing both arithmetic
and logical operations on the data.
A control unit, which could interpret an instruction
retrieved from the memory and select alternative courses
of action based on the results of previous operations.
The microprocessor can be referred to as the brain of the PC.
The microprocessor is also known as the CPU (Central
Processing Unit).
The microprocessor does the following:
1- Carries out commands to make the hardware components perform
actions.
2- Processes data. This involves:
- Performing logical instructions such as comparing
- Performing mathematical instructions such as adding
and subtracting
CPU
The CPU is the computer’s brain. This device does all of the
processing within the computer.
CPU stands for Central Processing Unit.
CPU speeds are calculated in terms of megahertz, this is known
as the system clock speed.
What is a hertz?
A hertz is a unit of measurement based on one second. It is what
is known as a frequency measurement. A frequency is something
that cycles from one point to another point.
Megahertz
The term mega can be considered approximately 1 million. So
therefore a megahertz will be approximately 1 million cycles
within one second.
The term megahertz is to identify CPU clock speed. It will
determine how fast that computer can process data.
For example a computer, which has a clock speed of
500MHz, can process 500 million bits of data within one
second.
MIPS (Millions of Instructions Per Second)
This measures the number of instructions a
microprocessor is capable of performing in a second. Once
again, the higher the number, the faster the processor.
The table below shows the main types of Intel
microprocessor (up to the Pentium MMX) with their speeds
measured in MIPS:
While clock speed is the most commonly used indicator of
performance, it does not always provide an accurate guide.
For example, a 486 processor with an internal clock speed
of 100Mhz will be slower than Pentium 90Mhz or even
75Mhz, due to their different internal architecture.
INPUT: Keyboard
OUTPUT: Printers
LASER
INK-JET
LASER PRINTERS
Prior to printing, an electrostatic charge is applied to a drum.
Then laser beam paths to the drum are altered by a spinning multisided
mirror.
The reflected beams selectively remove the electrostatic charge from
the drum.
Toner is deposited on these portions of the drum.
The drum is rotated and the toner is fused to the paper to create image.
INK-JET PRINTERS
Tiny droplets of ink, in either blue, red, yellow or black, are positioned
with great precision on the paper to form characters and images.
Movement of the print heads and paper are coordinated under program
control.