The three main internal components of a computer system unit are the central processing unit (CPU), motherboard, and memory. The CPU processes instructions and performs calculations. The motherboard houses and connects essential parts like the CPU, memory, ports, and expansion cards. Memory includes random access memory (RAM) for running programs, read-only memory (ROM) for basic settings, and cache to improve CPU efficiency. Other key internal components are the power supply, storage drives, cooling fan and heat sink, and ports for connecting peripherals. Specialized expansion cards provide network or graphics capabilities.

1. ND Unit 02
Computer Hardware
Internal components

2. Session Objectives
This session looks at what is inside the system
unit and what options you may have when
purchasing a new system.
1. You will learn to recognise these components
2. You will learn what these components do
3. You will learn where these components go
inside the system unit.

3. System unit components
We will look at the following system unit components:
Processor (CPU)
Fan and Heat Sink
Motherboard
BIOS
Power Supply
Hard disk drive – SATA, IDE,EIDE,master/slave
Ports – USB, parallel, serial
Internal Memory – RAM, ROM, Cache
Specialised cards
Network Interface Card (NIC)
Graphics Card

4. The Central Processing Unit (CPU)
The CPU is what truly defines a computer
It is the brain of the system & controls everything
It processes program instructions & performs
calculations
Speed is measured in GHz – the higher the number,
the faster the processor works

5. Fan and Heat Sink or cooling
Heat sink conducts heat away from CPU
Fins on heat sink warms air around it
Fan moves warm air away from heat sink
cooling the CPU

6. The Motherboard
Houses all the essential parts
Connects the parts with buses
Also, connections between the PC and peripherals
go through it

7. BIOS
Basic Input Output System
Accessed by pressing Esc, Del, F2 etc.
(depending on BIOS make/type)
usually on the ROM chip on Motherboard
checks the HW configuration
handles the input and output of the PC.

8. Power Supply
Converts Mains a/c (alternating current)
into d/c 5V or 12v (direct current)
Has a fan to stop overheating
Power(on/off)switch connected to front PC
On/Off switch sometimes way to reset PC

9. Hard Disk – storage
Programs and data are stored permanently on hard
disks
Hard disks are ‘Non-Volatile’ – nothing is lost when
the power is turned off
Hard disks are usually measured in Gigabytes

10. Internal Memory
RAM
ROM
Cache

11. RAM (Random Access Memory)
Programs are swapped into RAM for running
RAM is ‘Volatile’ – it loses data when the power is off
RAM is measured in bytes (more likely Gigabytes)
To preserve data /program instructions for later use,
they have to be stored in ROM or on a Hard Disk

12. ROM – Read Only Memory
Non-volatile - Stores data/settings when
power off
needed for when you turn on
Holds Hardware configuration, eg Hard
Drive BIOS settings, date and time etc

13. Cache Memory
Level 1 – Extremely fast memory
Level 2 - Very fast memory
L1 & L2 cache make the CPU more
efficient by reducing the waiting time of
the CPU when it communicates with RAM

14. Ports
Ports provide the link between peripheral
and the CPU
Parallel – transfers 1 byte (8 bits at a time)
Serial – transfers 1 bit at a time
USB – (Universal Serial Bus)
– A higher speed serial connection
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15. Specialised Cards
Network Card (NIC)
graphics card
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16. Network Interface Card (NIC)
Allows connection to a network
The type of NIC will vary with the topology and media
type in use
Many types exists. E.G. UTP NICS, Wireless, Fibre
Optic, On board, external (plugged in via USB port)

17. Graphics Card
This generates and outputs images to a display
Many offer added functions such as accelerated
rendering of 3D scenes and 2D graphics
High specification cards contain their own dedicated
RAM and processor (sometimes heat sink & fan too)