System unit

1. INSTRUCTOR : Hedayatullah “Adel”
Nangarhar Technical & Vocational Institute
System Unit Components
Lecture # 03
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2. System Unit
• System unit is a case that contains different electronic components of
the computer used to process data.
• System unit is made of plastic or metal to protect the components
inside it.
• The system unit typically contains motherboard, processor, memory,
hard disk and other electronic components.
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3. Motherboard
• Motherboard is a communication medium for the entire computer
system.
• It is the main circuit board inside the system unit.
• It is also known as system board often referred to as the mainboard
or ‘mono’.
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5. Motherboard Form Factor
XT (Extended Motherboard)
• Is a traditional slot type logic board introduced first in 1983 by IBM. It
had DIMM slots, 12 connector pins, ISA RAM expansion slots, and a
processor along with low insertion force.
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 AT Motherboard
• These motherboards have bigger physical dimensions of hundreds of
millimeters and hence they are not the right fit for the mini desktop
category of computers. Bigger physical size also inhibits installing new
drivers. Sockets and six-pin plugs are used as power connectors in
these motherboards. These power connectors are not that easily
identifiable and hence users face difficulties in connecting and using
it.
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 ATX Motherboard
• ATX denotes Advanced Technology Extended, it was developed by
Intel during the 1990s and it was an improved version over an earlier
version of AT motherboard. It is smaller in size when compared to AT
and it provides interchangeability of the connected components.
There is a marked improvement in the connector aspects.
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 LPX (Low Profile Extenstion) Motherboard
• Commonly used in slimline desktop computers in 1990s.
• Developed by Western Digital and is similar to the ATX.
• Lower profile and different arrangement of the components.
• Replaced by other form factors such as Mini-ITX and Micro ITX.
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 BTX (Balanced Technology Extened) Motherboard
• BTX denotes Balanced Technology Extended, intended to manage
demands of new technologies in terms of more power requirements
hence generation of more heat. Intel stopped further development of
BTX boards during the mid-2000s to concentrate on low power CPU.
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 Pico BTX motherboard
• These boards are smaller in size and hence the word Pico. Two
expansion slots are supported in spite of being sharing the top half of
BTX. Half-height or riser cards are its unique features and it supports
the demands of digital applications.
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 Mini ITX motherboard
• It’s a miniature version of motherboard over its earlier versions.
Designed in the early 2000s and its dimension is 17 x 17 cm. Mainly
used in small form factor (SFF) computer due to its lower power
consumption and faster cooling ability. This motherboard is the most
preferred in the home theater domain due to its lower level of fan
noise that will improve the quality of the theatre system.
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12. Components of Motherboard
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13. Components of Motherboard
Buses:
• A bus is an electrical path inside the computer system to transfer the
data and information form one part to other part.
• It allows the CPU to communicate with all devices.
• The amount of data that a bus can carry at one time is called bus width.
• The speed at which data moves from one component to another
component of the computer is called bus speed.
• Bus clock speed is measured in units of megahertz (MHz) or millions of
clock cycles per second.
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14. Components of Motherboard
• A computer may have three types of buses known as :
 System bus : it connects the processor to main memory.
 Backside bus : it connects the processor to cache memory.
 Expansion bus : allows the CPU to communicate with peripheral devices.
• Different types of system buses are as follows:
 Data Bus : is used to transfer data between different components of the computer.
 Address Bus : is used to connect the CPU with main memory to identify particular
addresses in main memory.
 Control Bus : is used to transmit different commands from one computer to another
component.
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15. Expansion Bus
• The buses that connect CPU to the peripheral devices are called expansion buses.
• Expansion buses are typically 16 to 64 bits wide and are mounted on motherboard.
• These buses connect CPU to expansion slot on motherboard to which external
devices may be connected.
• The common expansion buses include PCI and PCI Express (PCIe) buses, Universal
Serial Buss (USB) and FireWire.
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16. PCI Bus
• PCI stands for Peripheral Component Interconnect.
• PCI was originally developed to meet video demands of graphical user
interface. PCI is a high-speed 32-bit or 64-bit bus that is over 20 times
faster than ISA bus.
• PCI buses were widely used to connect CPU, memory and expansion
boards.
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17. PCI Express (PCIe) Bus
• The PCI Express (PCIe) bus is an expansion bus that doubles the speed
of the original PCI bus.
• PCI Express bus is used by almost all video cards, hard disks and
network cards.
• The ExpressCard technology used in traditional notebook computers
and tablet PCs also works with PCI Express bus.
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18. AGP Bus
• AGP stands for Accelerated Graphics Port. It is faster than PCI bus.
• It is dedicated to the acceleration of graphics performance.
• It is designed by Intel to improve speed of 3-D graphics and video
transmit.
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19. FireWire/IEEE 1394 Bus
• FireWire or IEEE 1394 is a high-speed bus standard developed by
Apple.
• It is typically used to connect multimedia devices like digital video
cameras to the computer.
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20. ISA Bus
• ISA stands for Industry Standard Architecture. It has been around
since 1984. It was developed for IBM personal computer.
• It is the most common and slowest expansion bus.
• ISA bus transmits 8 or 16 bits at one time.
• Mouse, modem card, sound card and low-speed network interface
card are connected to ISA bus directly or through ISA bus expansion
slot.
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21. CPU Fan Connector
• A motherboard fan connector is a small three or four-pin connector
located on the motherboard. The fan will have one set of cables
(bundled together) that will connect into the connector on the
motherboard.
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22. CMOS
• CMOS stands for Complementary Metal-Oxide Semiconductor.
• It stores configuration and information of computer. The information
include the type of disk drives, keyboard and monitor, current date &
time and other startup information required during booting process.
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23. EPS (Entry-level Power Supply) + 12V
• Power connector for the processor. This connector is characterized by
having 4 pins or 8 pins, which send the voltage to the VRM phases,
from where they are distributed to the processor.
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24. DIMM(Dual Inline Memory Module) socket / RAM slot
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• They are the RAM memory connection ports. This type of system is
quite simple, since we only have to move the lateral anchors and
'puncture' the RAM unit. When we insert it, the side anchors press on
the RAM and prevent it from moving.

25. SATA (Serial Advanced Technology Attachment) Connectors
• Data bus interface of modern computers that allows the connection
of storage devices and optical disc drives, among others.
• This type of interface offers high transfer speeds, supports longer
data cables, and hot plugging and unplugging drives.
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26. Motherboard Bridges
• 1. North Bridge :
North bridge is also called as Host Bridge. The north bridge is directly
connected to the Central Processing Unit(CPU) for processing tasks
that need the highest performance. These chip sets act as a medium
for communication between the CPU and parts of motherboard
thereby, Memory Controller Hub, being the other name for North
Bridge.
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27. Motherboard Bridges
2. South Bridge
• The south bridge is an IC on the motherboard responsible for the
hard drive controller, I/O controller and integrated hardware.
Integrated hardware can include the sound card and video card if on
the motherboard, USB, PCI, ISA, IDE, BIOS, and Ethernet.
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28. IDE (Integrated Drive Electronics)
• IDE (Integrated Drive Electronics) is an electronic interface standard
that defines the connection between a bus on a
computer's motherboard and the computer's disk storage devices.
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29. Power Connector
• This input is used to connect the output wire of the power supplyer
to the board, in fact, the power required by the motherboard and a
number of parts on it are supplied by this section.
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30. CPU Socket
• The processor socket (also called a CPU socket) is the connector on
the motherboard that houses a CPU and forms the electrical interface
and contact with the CPU.
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31. External motherboard
USB connectors
• The USB port has remained a universal standard and all modern
motherboards implement a large number of these.
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32. RJ45
• Communication interface for computer networks and internet
connection. It is characterized by having eight electrical connections
that are used as ends of twisted pair cables (UTP)
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RJ stands for :
Registered Jack

33. HDMI (High Definition Multimedia Interface)
• Video PC connector developed specifically for video output. This
connector usually appears in a large number of motherboards to take
advantage of the integrated graphics in the processor that integrates
it.
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34. Display Port
• Most advanced video interface that is characterized by allowing the
transfer of not only video, but also audio and data. It is also
characterized by being a free and unlicensed connector.
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35. VGA (Video Graphics Array)
• Classic video output that is being deprecated. One of its main features
is that it can be screwed to ensure the correct clamping of the
connector. Occasionally it can be seen on low-end motherboards and
on graphics cards it has already completely disappeared.
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36. COM Port
• It is commonly known as a serial port and this port is no longer used
or usually implemented on motherboards. This port was replaced by
the USB port, which offered better transfer rates and versatility.
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37. Parallel Port
• An interface that was used in home computers to connect a large
number of peripherals. This type of connector is also called a printer
port, since it was used by printers for many years.
Its main characteristic is that it could send several bits of data
simultaneously, which offered it greater versatility compared to serial
ports. This port was also replaced by the USB port.
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38. Audio Port
• Audio port is used to connect headphone, microphone and speakers
to the computer.
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39. Other ports
• MIDI Port : Musical Instrument Digital Interface, is used to connect
system unit to a musical instrument like: electronic piano keyboard.
• SCSI Port : Small Computer System Interface, used to attach SCSI
peripheral devices like disk drives and printers.
• Bluetooth Port : uses radio waves to transmit data b/w two devices.
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