Module 01
Computer Hardware
The Motherboard
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The spine of the computer is the motherboard, otherwise known as the system board (and less commonly referred to as the planar board).
This is an olive green or brown circuit board that lines the bottom of the computer. It is the most important component in the computer
because it connects all the other components of a PC together.
On the system board, you will find the following components:
Expansion slots
Memory slots
CPU and processor slots or sockets
Power connectors
On-board disk drive connectors
Keyboard connectors
Peripheral port and connectors
BIOS chip
CMOS battery
Jumpers and DIP switches
Chipsets
A chipset is a collection of chips or circuits that perform interface and peripheral functions for the processor. This collection of chips is usually
the circuitry that provides interfaces for memory, expansion cards, and onboard peripherals, and generally dictates how a motherboard talks
to the installed peripherals.
The functions of chipsets can be divided into two major functional groups: Northbridge and Southbridge.
Northbridge
The Northbridge subset of motherboard chipsets includes circuitry or chips that perform one very important function: management of high-
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speed peripheral communications. The Northbridge subset is primarily responsible for AGP communications and processor-to-memory
communications. Therefore, much of the true performance of a PC relies on the performance of the Northbridge chipset and its
communication with the peripherals it controls.
Southbridge
The Southbridge chipset, as mentioned earlier, is responsible for providing support to the myriad of onboard peripherals (PS/2, parallel, IDE,
and so on), managing their communications with the rest of the computer and the resources given to them. Most motherboards today have
integrated PS/2, USB, parallel, and serial ports.
The Southbridge chipset is also responsible for managing communications with the other expansion buses, such as PCI, USB, and legacy
buses.
Expansion Slots
The most visible parts of any motherboard are the expansion slots. These look like small plastic slots, usually from 3 to 11 inches long and
approximately 1/2 inch wide. As their name suggests, these slots are used to install various devices in the computer to expand its capabilities.
Some expansion devices that might be installed in these slots include video, network, sound, and disk interface cards.
If you look at the motherboard in your computer, you will more than likely see one of four main types of expansion slots used in computers
today:
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ISA
PCI
AGP
PCI Express
1. ISA Expansion Slots
2. PCI Expansion Slots
The ISA design is one of the most enduring elements of the PC. It
can be found on virtually all systems, from the second-generation
IBM PC to machines built today. However, it suffers from two major
shortcomings: lack of speed and compatibility problems stemming
from card design.
The PCI design's special bus and chip set are designed for advanced
bus mastering techniques and full arbitration of the PCI local bus.
This allows support of more than three slots.
The PCI bus has its own set of four interrupts, which are mapped to
regular IRQs on the system. If a PC has more than four PCI slots,
some will be sharing interrupts and IRQs.
Expansion cards must make use of system resources in an orderly
way, so that they do not conflict with other devices. When demands
for these system resources are not coordinated, the system could
behave erratically or even fail to boot up.
The PCI bus allows multiple bus-mastering devices.
Auto configuration lets the PC's BIOS assign the IRQ linking the card
to the system bus. Most PCI cards have no switches or jumpers to
set, speeding installation and preventing many hardware conflicts.
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3. AGP Expansion Slots
4. PCI Express
Accelerated Graphics Port (AGP) slots are becoming more popular. In
the past, if you wanted to use a high-speed, accelerated 3D graphics
video card, you had to install the card into an existing PCI or ISA slot.
AGP slots were designed to be a direct connection between the video
circuitry and the PC's memory. They are also easily recognizable,
because they are usually brown, are located right next to the PCI
slots on the motherboard, and are shorter than the PCI slots.
PCI Express or PCIe, (formerly known as 3GIO for 3rd Generation
I/O, not to be mistaken for PCI-X) is an implementation of the PCI
computer bus that uses existing PCI programming concepts.
A connection between any
two PCIe devices is known as
a "link", and is built up from a
collection of 1 or more lanes.
All devices must minimally
support single-lane (x1) links.
Devices may optionally
support wider links composed
of 2, 4, 8, 12, 16, or 32
lanes. This allows for very
good compatibility in two
ways. A PCIe card will physically fit (and work correctly) in any slot
that is at least as large as it is (e.g. an x1 card will work in an x4 or
x16 slot), and a slot of a large physical size (e.g. x16) can be wired
electrically with fewer lanes (e.g. x1 or x8; however it must still
provide the power and ground connections required by the larger
physical slot size). In both cases, the PCIe link will negotiate the
highest mutually supported number of lanes.
Processor Socket and Slot
Memory Slots
Memory or random access memory (RAM) slots are the next most
prolific slots on a motherboard, and they contain the memory chips.
There are varied types of memory are available for PCs today. PCs
today use memory chips arranged on a small circuit board.
These circuit boards are called Single Inline Memory Modules
(SIMMs) or Dual Inline Memory Modules (DIMMs), depending on
whether there are chips on one side of the circuit board or on both
sides, respectively.
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Aside from the difference in chip placement, memory modules also
differ in the number of conductors, or pins, that the particular
memory module uses. Some common examples include 30-pin, 72pin, and 168-pin (the 168-pin modules are most often DIMMs).
Additionally, laptop memory comes in smaller form factors known as
Small Outline DIMMs (SODIMMs).
Sockets and slots on the motherboard are plenty and varied.
Sockets are basically flat and have several rows of holes arranged in
a square. The processor slot is another method of connecting a
processor to a motherboard, but one into which an Intel Pentium II
or Pentium III.
On-Board Floppy and Hard Disk Connectors
On Board SATA connector
Most drives need a connection to the motherboard so the computer
can “talk” to the disk drive. These connections are known as drive
interfaces and are of two types: floppy drive interfaces and hard disk
interfaces. Floppy disk interfaces allow floppy disk drives to be
connected to the motherboard and, similarly, hard disk interfaces do
the same for hard disks. Most motherboards manufactured today
include both the floppy disk and hard disk interfaces embedded on
the motherboard.
Serial Advanced Technology Attachment(SATA) is an interface for
connecting hard drives to a computer.
Unlike IDE which uses parallel signaling, SATA uses serial signaling
technology. Because of this the SATA cables are thinner than the
ribbon cables used by IDE hard drives. SATA cables can also be
longer allowing you to connect to more distant devices without fear
of signal interference. There is also more room to grow with data
transfer speeds starting at 150 MB/s.
Keyboard Connectors
The most important input device for a PC is the keyboard. All PC motherboards contain a connector that allows a keyboard to be connected
directly to the motherboard through the case. There are two main types of keyboard connectors: AT and PS/2. The AT connector is round,
about 1/2 inch in diameter, and has five sockets in the DIN-5configuration.
The PS/2 connector is smaller and more common than the AT connector. Most new PCs you can purchase today contain a PS/2 keyboard
connector as well as a PS/2 mouse connector right above it on the motherboard.
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Peripheral Ports and Connectors
In order for a computer to be useful and have the utmost functionality, there must be a way for the data to arrive and depart. Many different
ports are available for this purpose.
Briefly, the seven most common types of ports you will see on a computer are serial, parallel, Universal Serial Bus (USB), Video, Ethernet,
Sound in/out, and Game ports.
Typical 9-pin and 25-pin serial ports
A Parallel Port
The above Figure shows an example of the two different types of
serial ports: 9-pin male and 25-pin male.
The above Figure shows a typical parallel port (also called a printer
port, because the most common peripheral connected to it is a
printer).
A Universal Serial Bus (USB) Port
A Video Port
Universal Serial Bus (USB) ports look slightly different, as shown in
the figure above.
Video (SVGA) ports (as shown above) are found on motherboards
that have built-in video circuitry to allow the computer to display
images on a monitor. The video port is typically a 15-pin, three row,
female connector.
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An Ethernet Port
A Game Port
If your motherboard has an Ethernet network adapter integrated
into its circuitry, you may see an Ethernet port (as shown above),
an RJ-45 port, attached to the motherboard.
The above figure shows an example of a game port (also called a
joystick port because that’s the most common device connected to
it). Game ports are used to connect peripheral devices to the
computer and use a 15-pin female connector.
Peripheral ports Directly Soldered to a Motherboard
Connecting a port to the motherboard with the Dongle
Method
The second method of connecting a peripheral port is known as the
direct-solder method. With this method, the individual ports are
soldered directly to the motherboard. This method is used mostly in
integrated motherboards in non-clone machines. Figure above
shows peripheral ports connected to a motherboard with the direct
solder method. Notice that there is no cable between the port and
the motherboard and that the port is part of the motherboard.
There are two ways of connecting these ports to the motherboard
(assuming the circuitry for providing these functions is integrated
into the motherboard). The first, called a dongle connection, allows
you to mount the ports into the computer’s case with a special
cable (called a dongle). The dongle for each port connects to the
respective pins on the motherboard for that port.
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