The three main components of an internal computer system unit are the processor, motherboard, and power supply. The processor acts as the computer's brain and carries out instructions. The motherboard brings all the components together and contains ports for adding peripherals. The power supply converts main power to lower voltages needed to run the computer safely.

1. INTERNAL SYSTEM UNIT
COMPONENTS
Olivia Johnson

2. PROCESSORS
The CPU (central processing unit) is the ‘brain’ of the computer. It carries out
instructions of computer programs, which is how they start up.
It also problem solves and performs basic logical and arithmetic operations.
Some processor chips can contain more than one CPU. These are called multi-core
processors.
The processor produces a lot of heat, so a fan and heat sink has to be attached.
Companies are developing lower voltage processors, so that less
heat is produced.

3. MOTHERBOARD
This is the main circuit board for the computer. It brings all
of the different components together, and contains ports that
you can add peripherals to.
It is called the motherboard because it is the main board, and
other circuit boards connect to it.

4. BIOS
BIOS stands for Basic Input/output System. This checks what
components are attached to the computer and whether they are
working. It also loads up the operating system.
The BIOS is a type of ROM, and it is stored on its own chip. You
cannot remove the BIOS, it is read only.
The BIOS generally doesn’t have a user interface, it is just codes.

5. POWER SUPPLY
The power supply unit (PSU) converts mains alternative
current into low voltage direct current, of either 12V or
5V.
PSUs have short circuit protection, as well as over
voltage and under voltage protection, to protect the
components from power surges.

6. FAN AND HEAT SINK
A heat sink transfers heat from the processor into the surrounding
air. It has ridges in it to maximise its surface area, in order to cool
more.
Most heat sinks are made of aluminium.
Fans usually sit on top of heat sinks, and circulate the air, allowing it
to cool more effectively.
A heat sink without a fan is called a passive heat sink, and one with a
fan is called an active heat sink.

7. HARD DRIVE
A hard drive (HDD) is a metal disk coated with magnetic
material that spins rapidly, with a magnetic head moving over it
to read and write data.
This is known as secondary storage, and it is where the user’s
files are kept.
There can be master/slave hard drives in a computer. These are
two different HDDs but one is in charge of the other, deciding
where data is kept.

8. PORTS
Ports are where you can add external components to a computer,
such as USBs. You have up to 127 devices connected via USB.
Ports can be for either input or output, for example, a keyboard
would be input and a monitor would be output.
There are other connections, such as parallel and serial ports.
A parallel port was used for printers and similar peripherals, and
serial ports are connections that only transfer one bit at a time.

9. INTERNAL MEMORY
ROM stands for Read Only Memory. This contains things like the BIOS, and other
things that the computer needs to run.
ROM holds its memory even when the computer is switched off.
RAM stands for Random Access Memory. This is volatile memory. When the
computer is switched off, it loses the data. RAM holds data so that it doesn’t have to
be loaded off the HDD all of the time, which means it doesn’t take as long to open
programs.
Cache is similar to RAM, but it is even faster. This stores data transparently.

10. SPECIALIZED CARDS
Graphics/video cards generate the output of images to a
computer screen.
Specialized cards are smaller circuits than the motherboard,
but they contain their own processor, BIOS and RAM.
Network cards allow connection to a modem or wireless
connection.