4.7.1.1 Internal Hardware Components
of a Computer
Internal Components
The internal components of a
computer system consist of the
hardware required to store and
process data, and communicate with
external (peripheral) devices
Main Internal Components:
Procesor
Main Memory
Input / Output Controllers
Internal components are
connected by the system
bus
The Processor
Sometimes refered to as the
CPU, the processor is the part
of the computer that
processes data by executing
program instructions.
The processor's program instructions
will be low-level instructions in the
form of machine code that the
processor has been designed to
handle, based on a specific processor
instruction set
For the processor to execute a program:
The program instructions need to be
transferred from secondary storage into
main memory
In main memory they can be decoded
and executed
The data that is needed is also loaded
into main memory from secondary
storage or provided by the input /
output devices
Main Memory
Memory that can be accessed directly by the
processor
Each memory location where
instructions or data are stored as
binary sequences, has a physical
address, which is a number used to
locate that memory location and
access its contents
There are two main types of main memory:
RAM
The 'working memory'
Used by the processor during the
Fetch-Decode-Execute Cycle
ROM
Used in the boot process for the
computer system
Input / Output Controllers
All external (peripheral) devices are connected to
the processor through I/O Controllers.
E.g. Secondary Storage Devices
In contrast to main memory,
Secondary Storage cannot be
accessed directly by the processor
Can also be described as
an interface between
the core computer
system and its
peripherals
Buses
The components of a computer system
are connected together using buses
Used to transfer data
System Bus
Address Bus
Used to specify the address of a
memory location to either read (i.e.
LOAD) data from or write (e.g. STORE)
data to that memory location.
Uni-directional
Bigger Width = Increased maximum memory capacity
Data Bus
Used to transfer data and
instructions
Bi-directional
Bigger Width = More data that can be fetched at one time
Control Bus
Used to send control signals that
manage and orchestrate
instructions/operations
Control Signals include:
Memory Read
Memory Write
Bus Request
Bus Grant
Bus Busy
Interrupt Request
Clock Signals
Bi-directional
One Way Conntections:
I/O Controller (Input) -> Data Bus
Data Bus -> I/O Controller (Output)
Processor -> Address Bus
Address Bus -> (ALL)
Two Way Conntections
Data Bus - I/O Controller (Sec. Storage)
Main Memory - Data Bus
Width
Refers to its number of parallel
lines.
This determines the number of
bits that can be transferred in
one operation
e.g. If the width of the bus is 8
bits, then 2^8 bits can be
transferred at one time