A+ Certification - ONE
Module 4
Motherboards
© 2009 N+S training!
A+ Certification - ONE
Module 4: Motherboards
Objectives
By the end of this module, you should be able to:
Name and describe the common desktop motherboard form
factors;
Understand the terms Northbridge and Southbridge;
Describe the contents of a motherboard BIOS chip
Run a BIOS setup programme;
Describe common BIOS setup programme options;
Clear a forgotten password from NVRAM (CMOS);
Flash a BIOS chip;
Recognize and describe the use of motherboard expansion
buses such as PCI, PCI-X, PCIe, AGP, USB, FireWire;
Recognize riser card slots (AMR, CNR, ACR);
Recognize memory card slots (SIMM, DIMM);
Understand CPU socket terminology (PGA, SPGA, LGA, ZIF);
Install a new motherboard.
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Module 4: Motherboards
Introduction
The motherboard (or system board) is the largest and most important
circuit board in a PC.
The motherboard provides sockets and slots for the attachment of a
CPU, memory cards, and add-on circuit boards called interface cards.
The motherboard also provides connectors (called ports) for the
attachment – via cables – of disks, keyboards, mice, printers, scanners,
sound equipment and so on.
All of the devices on a motherboard, or connected to it through a
socket, slot or port, are able to communicate with each other using the
buses built into the motherboard. In simple terms, buses are the circuits
that join the sockets, slots and ports together.
Form Factors
The size and shape of a motherboard and the position of its components
is defined by a form factor. Without form factors, fitting motherboards,
system cases and PSUs together would be unnecessarily complicated.
We will now look at some of the form factors that have been defined for
motherboards. We start with the ATX form factor and its variants,
which are probably the most common and widely adopted.
We will then look at the less widely used BTX and NLX form factors,
and then finally at a quite specialised form factor; ITX.
ATX Form Factors
ATX introduced several major
design changes to its predecessor;
AT.
The AT form factor used two 6-pin
connectors from the PSU to the
motherboard; the ATX form factor
has a one-piece, 20- or 24-pin
power connector known as P1.
© 2009 N+S training!
Figure 4.1 - AT Power Connectors
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The AT form factor had an on/off switch which was a direct cable
connection between a button on the front of the system case and the
PSU. ATX uses a cable from the front button to the motherboard, and
also supports soft-power; the ability to turn a PSU on or off by sending
signals to it as described in Module 3.
AT motherboards used a large, 5-pin
DIN connector for the keyboard, and
serial ports for mice. ATX replaced
these with smaller 6-pin DIN
connectors for both mouse and
keyboard.
Figure 4.2 - AT keyboard
connector
The ATX design provides the devices on the motherboard with better
spacing and improved air circulation than AT did.
Access to system components such as the CPU and memory banks was
improved, resulting in easier upgrades and maintenance.
Figure 4.3 – Micro-ATX Motherboard
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Module 4: Motherboards
Variations of the basic ATX ‘theme’ exist, including Micro-ATX,
Mini-ATX, Flex-ATX and EATX (Extended ATX).
BTX Form Factors
BTX is an Intel-led design. The BTX (Balanced Technology Extended)
form factors were intended as the replacement for the ATX form factors
in desktop systems, they were introduced in late 2004. They have not
been widely adopted, and Intel themselves stopped development of
BTX retail products in September 2006.
Figure 4.4 – MicroBTX Motherboard
Therefore you are only likely to see BTX motherboards and system cases
in older pre-built systems.
The BTX design reduced internal heat in the PC by presenting fewer
obstacles to the airflow produced by the PC’s fans.
The position of the mounting points for the motherboard was improved
to reduce the physical strain caused by the increase of heavy cooling
devices (heatsinks, fans etc).
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The power connectors on a BTX motherboard are the same as ATX, so
they should work with ATX design PSUs. However, due to the
repositioning of the mounting points, BTX motherboards require a BTX
form factor compatible system case.
There are three main variants of BTX motherboard; BTX, Micro-BTX and
Pico-BTX.
NLX Form Factor
Intel developed the NLX as the
form factor intended to replace
all others, although this never
happened and NLX has been
superseded by the ATX and ITX,
and production of NLX
motherboards has ceased. NLX
was characterised by a modular
design that allowed fast access
to system components; no
screws need be removed as
each component module could
simply be unclipped and/or
lifted out.
Figure 4.5 - NLX Motherboard
NLX motherboards have their bus slots mounted on a riser card (or
daughterboard). Interface cards are inserted into the riser card so that
they are on the same plane as the NLX motherboard rather than at rightangles to it. This allows an NLX motherboard to use low-profile system
cases.
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Module 4: Motherboards
ITX Form Factors
The ITX form factor was
introduced into the marketplace
by VIA technologies in 2003.
There are three types of ITX
motherboards at this time;
Mini-ITX which are 170 x 170
mm and Nano-ITX which are
120 x 120 mm – about the same
size as a CD-ROM case.
Most ITX motherboards do not
use standard Intel CPUs; instead
they have VIA CPUs. Even so,
they are still capable of running
standard PC operating systems.
Regardless of their size, ITX
motherboards are full of
features. Most will provide
connectors for IDE devices
(although 2.5‛ hard disk drives
and special slim line CD/DVD
drives may need to be used),
USB and FireWire ports for
connecting peripherals, a PS/2
keyboard and mouse port,
Ethernet ports for connecting to
a LAN (Local Area Network), a
VGA port for attaching a
monitor, and built in sound
cards.
© 2009 N+S training!
Figure 4.6 - Mini-ITX
Figure 4.7 - Nano-ITX
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Module 4: Motherboards
There is an even smaller
Pico-ITX variant, which is a
mere 100 x 72mm in size.
A PC based around an ITX
motherboard would be perfectly
capable of running Windows XP
or Vista and Microsoft Office
applications, browsing the web
and playing multimedia files.
Figure 4.8 - Pico-ITX
However, ITX (especially Pico-ITX) is really intended for more
specialised situations, such as in-car entertainment systems.
The following table shows relative motherboard sizes (sorted by total
surface area). It is purely for interest, you do not need to revise this for
the A+ exam.
Table 4.1 – Motherboard size comparison
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Name
Size
Extended ATX
330 x 305 mm
BTX
325 x 267 mm
ATX
305 x 244 mm
Micro-BTX
267 x 264 mm
Micro-ATX
244 x 244 mm
Mini-ATX
284 x 208 mm
Pico-BTX
267 x 203 mm
Flex-ATX
229 x 191 mm
Mini-ITX
170 x 170 mm
Nano-ITX
120 x 120 mm
Pico-ITX
100 x 72 mm
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Module 4: Motherboards
Summary
A motherboard’s form factor defines its shape and size, the position
of its ports, connectors and slots, and the type of power supply
required. In addition to this, the form factor defines where the
mounting points are positioned for fixing the motherboard to the
system case. For this reason, the motherboard’s form factor also
defines what type of system case and PSU need to be used.
Common motherboard form factors include ATX, BTX, NLX and ITX.
Chipsets
Each component of the motherboard has its own particular task to
perform; the CPU performs arithmetical and logical operations on data;
RAM acts as a high-speed temporary storage area for data; the
expansion buses carry data from one place to another; input and output
devices store, retrieve and display data. The function of the chipset is to
ensure that all of these components are able to communicate with each
other in a controlled, reliable and efficient manner.
The chipset may also be able to perform other functions, such as
controlling fan speeds in order to manage temperatures.
Chipsets are an integral part of the
motherboard and are therefore not usually
upgradeable and are hard-wired to the
motherboard. Should your chipset develop a
fault, this will usually require a replacement
motherboard.
Modern chipsets are working at very high
speeds; therefore they are usually covered by
a heatsink that draws the heat away from the
chip to assist cooling.
Figure 4.9 - Chipset with
Heatsink
There are hundreds of different models of chipset made by Intel, AMD,
VIA and others. It is unlikely therefore that you will be asked specific
questions about any particular chipset in the A+ exam.
However, here are some examples of chipsets and their capabilities
which highlight the points made above.
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Processor Support
Chipset
Category
CPU support
No of CPUs
945GT
Desktop
Core 2 Duo
1
GM45
Laptop
Core 2 Duo
Core 2 Quad
Core 2 Extreme
1
E8870
Server
Itanium
1-4
System RAM Support
Chipset
Category
RAM support
Amount of RAM
945GT
Desktop
DDR2
4 GB
GM45
Laptop
DDR2
DDR3
8 GB
E8870
Server
PC1600 DDR
128 GB
Bus / Device Support
Chipset
945GT
GM45
E8870
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Graphics
PCIe x16
PCIe x16
PCI/PCI-X
Bus slots
PCIe x1
PCIe x1
PCI/PCI-X
SATA
2 devices
4 devices
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PATA
2 devices
2 devices
4 devices
USB
8 x 2.0
12 x 2.0
6 x 2.0
© 2009 N+S training!
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Module 4: Motherboards
Chipset Structure
Many chipsets have two distinct
parts. These are called the
Northbridge and Southbridge (by
AMD, VIA and others), or the
Memory Controller Hub (MCH)
and I/O Controller Hub (ICH) by
Intel.
The Northbridge (or MCH)
controls the CPU, system RAM,
and AGP or PCIe video bus; the
Southbridge (or ICH) controls the
slower I/O buses, such as PCI,
IDE, SATA, and USB.
Figure 4.10 - Intel G41 “Northbridge”
and ICH7 “Southbridge”
Below is an example block diagram of how a typical chipset might be
structured.
Figure 4.11 – Northbridge (MCH)/Southbridge (ICH) Structure
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Summary
Chipsets contain the logic to support a particular combination of
devices. The devices supported by the chipset include; CPU,
system RAM, and expansion buses.
Many chipsets are divided into two ‘sections’; each with their own
areas of responsibility. These two sections are referred to as the
Northbridge and Southbridge or the Memory Controller Hub (MCH)
and I/O Controller Hub (ICH) respectively.
BIOS
The motherboard BIOS (Basic Input Output System) consists of a ROM
chip which has programme instructions built into it. This is why you
may hear it referred to as both ‚the BIOS‛ (meaning the software), or
‚the BIOS chip‛ (meaning the hardware).
Note: Software programmes embedded into a piece of hardware are
also known as firmware.
There are different types of ROM that your BIOS chip may be made
from. However, the differences between them are not really important
to know, as you are unlikely to need to change any of the ROM chips
on your motherboard or interface cards. But purely as a matter of
interest, a description of different ROM technologies is provided below.
PROM
A Programmable Read-Only Memory (PROM) is a form of ROM where
the setting of each bit (0 or 1) is permanently set by a fuse or anti-fuse.
The memory can be programmed just once after manufacturing by
blowing the fuses (using a device called a PROM blower), which is an
irreversible process. Blowing a fuse opens a connection while blowing
an anti-fuse closes a connection. BIOS chips made from PROM would
only be found in extremely old motherboards. Motherboards using
PROM chips may therefore only have their BIOS updated by replacing
the entire chip.
EPROM
An Erasable PROM (EPROM) chip’s bits are made of memory cells that
act like permanently open or closed transistors. When the memory cell
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Module 4: Motherboards
is charged, it holds the charge until it is erased using ultraviolet (UV)
light.
A programmed EPROM retains its data for
about ten to twenty years and can be read an
unlimited number of times. An erasing
window must be kept covered to prevent
accidental erasure by the UV in sunlight.
Old PC BIOS chips were often EPROMs, and
the erasing window was often covered with a
label containing the BIOS publisher's name,
the BIOS revision, and a copyright notice.
Like PROM chips, EPROM chips can only be
updated by replacement.
Figure 4.12 – EPROM
with Label Removed
Flash ROM
Flash ROM is a development of
the EEPROM (Electrically Erasable
Programmable ROM) chip.
Unlike PROM and EPROM
memory, flash ROM can be
updated by electrical signals sent
to it by the motherboard.
Figure 4.13 - Hardwired flash ROM
Flash ROM chips may be
hardwired (soldered onto the
motherboard) or inserted into a
PLCC (Plastic Leaded Chip Carrier)
socket.
All modern motherboard BIOS
chips are flash ROM, making them
easy to update.
Figure 4.14 - PLCC flash ROM
All that needs to be done is to obtain the appropriate BIOS update
programme (usually by downloading it from the manufacturer’s web
site) and then execute it.
Flash ROM has uses apart from motherboard BIOS chips. Memory
cards for cameras and USB pen drives also use flash ROM. These
devices are discussed in depth in later modules.
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BIOS Chip Contents
Although the programmes built into the chip are referred to as a single
entity – the BIOS – they are in fact a collection of programmes which
includes the POST, the bootstrap, hardware access routines and a setup
utility. We will now examine these BIOS components.
POST
When a PC’s PSU is turned on there will be a short delay before stable
voltages are being provided. Once stable power has been established
by the PSU, the PSU will send a ‚power OK‛ signal to the CPU (this is
sent via pin 8 on an ATX P1 power connector). This ‚power OK‛ signal
causes the CPU to start executing a programme from the motherboard
BIOS chip called the Power On Self Test (POST).
The POST checks that the vital devices in the PC
– such as memory, keyboard, and video card –
are functioning correctly. If any of these devices
are faulty, the POST will give an error message
indicating the fault.
POST error messages are given either as beeps
from a small speaker on the motherboard or as
messages on the screen.
If there are no faults, then another programme in
the BIOS chip is executed that searches the PC
looking for an operating system; this programme
is called the bootstrap.
Figure 4.15 Motherboard Speaker
Bootstrap
The bootstrap is responsible for searching through a sequence of
devices in your PC in order to locate your operating system.
The type of device that the bootstrap may search depends on the
manufacturer of the BIOS. Typical bootable devices include floppy
disks, optical disks, hard disks and USB flash drives; some bootstrap
routines may be able to boot from other devices such as network
interface cards. The order in which these devices are searched can be
set by the user; this is discussed shortly.
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When the bootstrap finds a device that it can boot from, it loads the
programme code from a special part of that device, called the boot
sector, into system RAM. This boot sector code will then take over
control from the BIOS and continue loading the rest of the operating
system from that device into system RAM.
Hardware Access Routines
These BIOS routines are analogous to operating system device drivers;
they are routines that may be used to provide communication with and
control over specific pieces of hardware.
When the PC is initially turned on there is no operating system such as
Windows or Linux present to allow the user to control the PC and
interact with its hardware devices. The hardware access routines
provide this functionality instead.
Sometimes the hardware access routines in the BIOS will be used by
Windows or Linux once it has booted, but normally the operating
system will use its own specific device drivers.
The BIOS Setup Utility and BIOS Settings
In order to function properly, the BIOS routines need information about
the specific configuration of the PC – eg the types of drives that are
installed in the PC, and the order in which they should be searched by
the bootstrap. This machine-specific information is kept in a special
part of the BIOS chip called NVRAM (non-volatile RAM).
Formerly this information was held in a separate RAM chip on the
motherboard called the CMOS (Complementary Metal Oxide
Semiconductor).
Because CMOS memory was RAM, and
therefore volatile, it required battery power in
order to maintain its values. Nowadays the
only function of the battery is to maintain the
PC’s real-time clock (ie current date and
time). Confusingly, many texts will still refer
to CMOS settings rather than BIOS settings,
even though these settings are no longer
actually held in a separate CMOS chip.
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Figure 4.16 – CMOS
Battery
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BIOS settings are created using another program stored in the BIOS
chip; the BIOS setup utility.
During the first few seconds of a PC’s boot process you will be able to
press a key, or combination of keys, to enter the BIOS setup utility. The
actual keystroke(s) will depend on the version of the BIOS being used.
Most systems will display a message indicating how to enter the set-up
utility. However, the message may only be displayed very briefly. The
Del, Esc, F1 and F2 keys are among the most commonly used.
Once the set-up utility has been invoked, a menu of options is
displayed, allowing configuration changes to be made. The available
options will vary from BIOS to BIOS – some of the most common are
shown below.
Figure 4.17 - BIOS Setup Utility
In Figure 4.17, you can see typical settings that can be adjusted using a
BIOS setup utility. You should be aware that some BIOS setup utilities
will not provide all of the options shown, and others may provide extra
options.
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Boot Sequence
This specifies the order in which the system tries to locate a boot device
(a device that contains an Operating System).
It is wise to set the boot sequence so that the PC’s optical drive is
searched before the hard disk drive. This makes it easier to boot from
an emergency disk, such as the Windows installation CD, should there
be a problem with the hard disk drive.
Figure 4.18 – Boot Sequence
Hard Disk(s)
This setting holds information about the PC’s hard disks such as the
access modes that they support. This information is normally detected
automatically and does not require manual setup by the user when a
new disk is added.
Figure 4.19 - Disk Settings
Date and Time
This option allows the system date and time to be set, although this is
usually changed from within Windows.
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Figure 4.20 - Date/Time
Password
This setting allows a power on password, often referred to as a User
password to be set on the computer. This feature can be useful to
prevent unauthorised use of the PC, especially if it is being used in a
public place. Another password, often called a Supervisor password,
can be set to protect the BIOS setup utility from unauthorised use.
Figure 4.21 – Password Settings
Anti-Virus Protection
Many BIOS setup utilities protect hard drives from viruses. This
protection is very basic and will typically only protect a special area of
the hard disk drive called the boot sector. You should also run normal
anti-virus software, such as Norton or McAfee, to protect the other files
on your hard disk drive.
Clock speeds
Some BIOS programmes allow the speed of the system clock to be
altered. This may need to be changed if for example a faster CPU is
being installed.
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Built-in devices
Any devices built into the motherboard may have an option to disable
them in the BIOS. Such devices may include parallel ports, serial ports,
USB, and video.
These disable options may be used to suppress error messages given by
faulty devices, or to disable a device that has been replaced by the
addition of an interface card. Motherboard devices may be replaced by
interface cards if they have become faulty, or a newer type needs to be
installed.
CPU Settings
Some BIOS programmes allow certain internal features of the CPU to be
enabled or disabled. This could include Hyperthreading, MMX and SSE
(you don’t need to know what these are yet, just that they are CPU
features that can be enabled or disabled in the BIOS).
Clearing BIOS Settings
Sometimes it is desirable to clear information from the BIOS NVRAM.
Let’s say for example that a user has set a power-on password using the
BIOS setup utility, but has now forgotten the password, and is now
locked out of the PC.
The password could be cleared on
old motherboards by removing the
CMOS battery for a few minutes
and then re-inserting it. As
modern PCs use BIOS NVRAM to
store this type of information, they
provide a jumper on the
motherboard to perform this
function. This jumper is normally
near the motherboard battery, and
is often marked as CLR CMOS or
CLR PWD.
Figure 4.22 - Clear Password jumper
BIOS Upgrades
Originally, the only method of upgrading the BIOS was to replace the
BIOS chip or the whole motherboard; this was because the BIOS was
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stored in a PROM or EPROM chip. Storing BIOS programs in flash
ROM allows them to be updated while in situ by simply running a
program (a process often referred to as flashing the BIOS).
To upgrade BIOS, all that you need to do is download the required files
from the website of your motherboard or PC manufacturer. Your
manufacturer may be able to send you these files on disk should you
not have Internet access.
Once these files are downloaded,
you may need to:
a)
Copy the files that you
have downloaded to a
bootable floppy disk and
then reboot from the
floppy, or
b) Run a BIOS programme
by pressing a key when
the PC is booted up which
will then perform the
update using the files from
the floppy, or
c)
Simply run the
downloaded programme
by double-clicking on it
directly from within your
Windows system as
shown on the right.
Figure 4.23 - Flashing a BIOS
It may also be necessary to change a switch or jumper setting on the
motherboard, to allow the upgrade program to access and update the
BIOS.
So why would you want to upgrade the BIOS? New technologies are
emerging in the PC market all of the time. The BIOS in some PCs may
not handle newer technologies; to do so, the BIOS may need to be
upgraded. Or, the programmes in the BIOS chip may simply have a
bug that needs to be fixed.
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Flashing is relatively straightforward, but any problems – such as a
power failure during the flashing process – can result in the BIOS being
corrupted, causing the motherboard to stop working altogether.
So whenever flashing BIOS you should always take the following
considerations into account.
Never interrupt the BIOS update.
Never perform a BIOS update on a laptop running from
batteries; always plug the laptop into the mains.
Always read the manufacturer’s website or manual for the exact
instructions to perform a BIOS upgrade on your motherboard.
To guard against the possibility of
complete failure, some
motherboards now carry a
redundant ROM chip with a copy
of the BIOS, which transparently
takes over should the main BIOS
chip become inoperable because
of a failed BIOS update, and
provides the user with the means
of repairing the primary BIOS
chip.
Figure 4.24 - Dual BIOS chips
In addition to the motherboard BIOS chip, other devices such as your
video card and printer may allow their firmware to be updated. It is
worth checking the manufacturer’s website for these updates on a
regular basis.
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Summary
The BIOS chip is a ROM chip on the motherboard.
The BIOS chip holds system-level programs. These include:
A setup program
A power-on self-test (POST) program
Hardware access routines
The setup program creates a configuration of the PC’s hardware. The
configuration is stored in the BIOS chip’s NVRAM (or in a CMOS
RAM chip on very old motherboards).
The POST program detects and reports hardware faults when the PC is
turned on.
The Basic Input/Output System provides communication with, and
control over, the motherboard’s devices.
The BIOS setup program is invoked by pressing a key when the PC is
booted. This key may be Del, Esc, or a function key.
Expansion Buses
Expansion buses allow features to be added easily to the motherboard.
Expansion buses provide slots, into which circuit boards referred to as
interface cards can be added. Modern motherboards provide so many
features that there is less need to use interface cards than there was in
the past. Nevertheless, expansion bus slots may be useful if you require
something more powerful than the motherboard provides, or a feature
not present on the motherboard, such as a TV tuner card, or a
sophisticated video card for game playing.
PCI
PCI (Peripheral Component Interconnect) was developed by Intel,
Compaq and Digital, but it is now under the control of a consortium of
companies called the PCI-SIG (PCI-Special Interest Group).
PCI is occasionally referred to as PCI conventional, as other versions
such as PCI-X and PCIe have been introduced.
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PCI slots may vary in the number of bits that they carry per transfer (32
or 64-bit), the speed at which these transfers occur (33 or 66MHz) and
the voltage that they use (3.3 or 5V). Some of these combinations
however are rarely used.
Practically all desktop PC motherboards
use only 32-bit, 33MHz, 5V slots, as
shown in Figure 4.25.
These slots can easily be identified
visually. They are invariably made of
white plastic, and have a short section
of connectors furthest away from the
back edge of the motherboard.
Figure 4.25 - PCI 32-bit slots
Obviously, 32-bit/33MHz/5V PCI cards will work in these slots. The
edge of the card will be exactly the same shape as the slot; an example
is shown in Figure 4.26.
There is another type of card that will work in these slots which are
32-bit/33MHz/universal voltage cards. These types of cards will work
in both 5V and 3.3V slots; an example is shown in Figure 4.27.
Note: Although PCI includes a specification for 32-bit/33MHz/3.3V
slots, they are hardly ever found in PC motherboards.
Figure 4.26 – 5V PCI 32-bit card
Figure 4.27 - Universal Voltage PCI
32-bit card
PCI-X
PCI-X (eXtended) is a 64-bit version of PCI. It is almost never seen built
into anything except server motherboards.
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The most common implementation of PCI-X transfers 64-bits at
66 MHz, 100 MHz or 133 MHz using 3.3V signalling.
Clock speeds of 266 MHz or 533 MHz are part of the standard, but are
rarely implemented. This is because PCIe slots are proving to be a more
popular choice with manufacturers.
To cater for the extra data bits and associated control signals, PCI-X slots
are longer than PCI conventional 32-bit slots.
The next figure (Figure 4.28) shows a server motherboard with 6 PCI-X
slots. From top to bottom, the first four slots are 66 MHz/64-bit/3.3V.
The fifth slot is 100 MHz/64-bit/3.3V, the sixth slot is
133 MHz/64-bit/3.3V.
You can see that there is no physical difference between the slots,
which is why they are so clearly marked on the motherboard. Inserting
a 133 MHz card in a 66 MHz slot (or vice versa) would cause no
damage. But the card/slot would run at whichever is the slower of the
two speeds (eg a 133 MHz card in a 66 MHz slot would run at
66 MHz).
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Figure 4.28 - PCI-X motherboard
Notice also that the shortest section of connectors is nearest the back
edge of the motherboard (on the right of the figure). This prevents a 5V
card from being inadvertently inserted in the slot.
As you can see, the manufacturer of this motherboard has provided only
64-bit slots. So, what if you needed to add a video capture card, for
example, but the only model you could find or afford was a
conventional 32-bit PCI card? Well, as long as the card was 3.3V or
universal voltage, it would work in any of the slots above, but at the
slower rate. So, if plugged into the first of the six slots above, the card
would work at 33 MHz/32-bit.
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PCIe
PCI Express (officially abbreviated as PCIe) was
introduced in 2002 and looks like it will
eventually replace PCI and PCI-X entirely.
PCIe slots are not compatible with PCI or PCI-X
cards and vice-versa.
Figure 4.29 - PCIe Logo
This is because PCIe uses an entirely different form of data transmission.
PCI and PCI-X transmit data 32 or 64 bits at a time in parallel. The PCIe
bus transmits bits serially across pairs of wires (one to transmit, one to
receive) called ‘lanes’. Each lane provides bi-directional transmission of
bits at different clock speeds depending on the version of PCIe
implemented on the motherboard. PCIe 1.x uses a clock speed of
1.25 GHz, 2.0 uses 2.5 GHz and 3.0 uses 4 GHz.
Lanes can either be used singly or in groupings of 2, 4, 8, 16 or 32
lanes. These variations are referred to as x1, x2, x4 etc. As the number
of lanes is increased, so is the size of the expansion slot on the
motherboard.
The figure below shows some PCIe slots, from top to bottom they are,
PCIe x4, PCIe x16, PCIe x1, PCIe x16 and finally a conventional 32-bit
PCI slot.
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Figure 4.30 - PCIe x4 and x16 Slots
Although the raw transmission speed of PCIe is 2.5 Gbps per lane,
clocking information is transmitted with the data that effectively reduces
the payload (the amount of actual data transmitted) to 80% of the
bandwidth.
So, for PCIe x1 we have 1 lane, carrying data at 2.5 Gbps in each
direction. The payload will be 80% of this bandwidth, giving us 2 Gbps
(256 MBps).
PCIe x16 would give us 16 times this bandwidth, which is 32 Gbps
(4096 MBps).
Summary
The most commonly used form of PCI conventional is 32-bit/33
MHz/5V.
PCI-X is a 64-bit version of PCI. It is found almost exclusively on
server motherboard.
Both PCI and PCI-X are being replaced by PCIe.
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AGP
Modern PCs place high demands on the display system that require
transferring large amounts of information from the PC’s memory to the
video card very quickly; this in turn requires a bus with a high
bandwidth.
Prior to AGP (Accelerated Graphics Port), video cards were connected
to the PCI bus, therefore limiting them to the PCI conventional
bandwidth which at the time was 133 MBps (33.3 MHz * 32 bits =
1066.6 Mbps. 1066.6 / 8 = 133 MBps). In addition, PCI video cards
had to compete for this bandwidth with any other devices connected to
the PCI bus.
AGP is in a dedicated video bus;
only the video card is connected
to it, so the card does not have to
compete with other data transfers.
It offers high speed data transfer
using a 32-bit bus running at 66
MHz.
AGP is able to transfer data once,
twice, four or eight times per clock
cycle. These variations are called
AGP 1x, 2x, 4x and 8x
respectively.
Figure 4.31 - AGP Video Adapter
The table below shows the bandwidths provided by these variations of
AGP. As you can see, even AGP 1x – the slowest version of AGP –
provides 266 MBps; twice the bandwidth of the conventional
32-bit/33 MHz PCI bus.
Table 4.2 - AGP bandwidths
Standard
Width
AGP 1x
32
66
1
2133
266
AGP 2x
32
66
2
4266
533
AGP 4x
32
66
4
8533
1066
AGP 8x
32
66
8
17066
2133
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These higher bandwidths make AGP more suitable for high resolutions
and colour depths.
AGP also provides the ability to read and write simultaneously to video
memory and contains features in its chipset that improve the
performance of applications that use 3D texturing and rendering. These
features are very important if you play a lot of games on your PC, they
are not so important for general office work.
An AGP slot is visually similar to a PCI expansion slot. It is however set
deeper into the motherboard, so cannot be used by PCI expansion
cards.
In the figure below, the AGP slot is at the bottom, set slightly back from
the three PCI slots (ie further away from the edge of the motherboard).
Figure 4.32 - AGP Slot
AGP is being replaced by PCIe x16 slots for video cards in new
motherboards. The fastest version of AGP (8x) provides 2133 MBps
compared to PCIe x16’s 4096 Mbps.
Summary
AGP is a bus specially designed for video cards.
AGP only provides a single expansion slot, compared with the multiple
slots provided by PCI that can accommodate video cards, sound cards,
modems etc.
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USB
The standard parallel and serial ports on a PC are being gradually
replaced by the introduction of the Universal Serial Bus (USB). The
advantages of USB are shown below.
Hot Plug and Play Connections – Connecting a USB device is simply a
matter of plugging the device in to a USB port; Hot Plug and Play
means this can be done while the PC is turned on and the operating
system is running. The operating system will automatically recognise
the device and install its drivers.
Fast Data Transfer Rates – USB 1.1 offers
two data transfer rates; 1.5 Mbps (Low
speed) for devices with low bandwidth
requirements such as mice, and 12 Mbps
(Full speed) for other devices such as ADSL
modems. USB 2.0 supports a data transfer
rate of 480 Mbps (60 MBps) known as Hi
speed in addition to Low and Full speed.
These speeds compare very favourably
with the maximum serial port speed of 0.1
MBps and the maximum parallel port
speed of 5 MBps.
Figure 4.33 - USB 1.1 Logo
Figure 4.34 - USB 2.0 Logo
Therefore it is likely that serial and parallel ports will eventually
disappear, and indeed many manufacturers are producing
motherboards with USB ports only.
Variety of devices – There is an enormous variety of USB devices
available, including printers, keyboards, mice, ADSL modems, hard
disk drives, external CD/DVD drives, scanners, cameras, speakers,
tape units, monitors, flash memory cards and pens, MP3 players, WiFi
adapters and even desk fans, lights, miniature vacuum cleaners and
mug warmers.
The starting point of a USB bus is called a host controller. The host
controller contains a component called a root hub that provides one or
more USB ports.
The host controller, its root hub, and the root hub’s USB ports are
usually built into the motherboard. A motherboard may have one or
more host controllers built into it.
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Figure 4.35 –USB Host Controllers
Each USB bus can accommodate up to 127 devices. Devices are
connected in an asymmetrical tree topology. You can think of this like
a family tree, where hubs are parents, and devices are offspring. At the
top of the tree is the host controller with its root hub and ports; the
‘Adam and Eve’ of the USB bus.
Each port on the root hub may have either a USB device such as a
printer plugged into it, or an external hub. Plugging one hub into
another is referred to as cascading a hub. External hubs are used to
increase the numbers of ports available. External hubs may either be
active or passive. The ports on an active USB hub can provide power
to the devices plugged into its ports, as the hub is connected to a mains
power supply. Passive hubs provide no extra power from their ports.
The number of extra ports provided by an external USB hub may be
anything from 2 to 7 ports.
Figure 4.36 - Passive 4-Port USB Hub
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Figure 4.37 - Active 4-Port USB Hub
Webcam
Mouse
Hub
Camera
Printer
Scanner
DVD
Figure 4.38 - USB Asymmetrical Tree Topology
In the Figure 4.38 above, the PC has a USB host controller with a 4-port
root hub built into the motherboard. Plugged into two of the ports are a
mouse and a webcam. Plugged into the third port is a cascaded 4-port
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external hub. Plugged into the external hub are a printer, scanner, DVD
drive and camera.
USB Power
The USB root hub can provide electrical power to peripherals. The root
controller has a built-in 5 V power distribution scheme (500 mA per
port). Some devices, such as keyboards and mice, can draw all the
power they need from the hubs, others such as DVD drives and hard
disks may need to be plugged into the mains power supply.
Tools such as Windows XP Device Manager can display the amount of
power used by each device on the USB hub and the amount of power
available.
Figure 4.39 - USB Power
Hubs may or may not have their own power supply, but hubs that have
other hubs cascaded from them must be powered.
As a troubleshooting technique, if a USB device does not appear to be
functioning, check to see if it receiving enough power from the bus by
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removing any other unneeded USB devices; this may make enough
power available for the failed device to function.
USB Connectors
There are two types of USB connector – A and B, both of which have a
female (port) and male (plug) equivalent.
USB A ports are found in hubs. USB B ports are found in larger USB
devices such as printers and scanners. USB mini-B ports are built into
smaller devices such as cameras and external hard disk drives.
Some devices do not have a port at all, as their USB cable is directly
connected to them; mice and keyboards are examples of this.
Figure 4.40 - A Port
Figure 4.41 - B Port
Figure 4.42 - Mini-B Port
USB plugs are found at the ends of USB cables. USB provides A, B and
mini-B plugs to match the ports described earlier. There are now also
USB micro ports and plugs; these are the same width as their mini
equivalents but they are slimmer, being less deep. They are typically
used on mobile phones.
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Figure 4.43 - A Plug
Figure 4.44 - B Plug
Figure 4.45 - Mini-B Plug
So for example, to connect a USB camera to a PC, you would use a
cable with an A plug at one end and a mini-B plug at the other. The A
plug would connect to the PC’s A port; the mini-B plug would connect
to the camera’s mini-B port.
USB Cables
The maximum length of a single USB cable is officially 5 metres.
However, individual cables can be used to interconnect powered USB
hubs. Using this arrangement, up to 5 hubs can be cascaded
(connected together), allowing the furthest device to be up to 30 metres
away from the PC.
PC
Hub
Hub
Hub
Hub
Hub
Distance from PC to printer joined by 6 x 5 metre cables – 30 metres
Figure 4.46 - USB Cable Distances
Installing USB devices
Installing a USB device is simply a matter of plugging the device in.
USB devices themselves do not require system resources such as IRQs
and I/O addresses; only the root hub requires these. The only
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requirement is that the device is connected to a USB port using a cable
with the relevant plugs at either end, and to a mains supply if required.
The first time that a USB device is connected to a PC, a driver may have
to be installed. If Windows cannot locate the driver automatically, it
will prompt you to specify the location of the driver using the Found
New Hardware Wizard:
Figure 4.47 - Found New Hardware Wizard
Removing USB Devices
USB devices are hot-swappable; they can be connected, and
disconnected, while the PC is turned on.
However, be aware that some USB devices
should be ‘stopped’ before they are
disconnected. Stopping USB devices is done
using the Safely Remove Hardware icon in
Windows’ notification area of the taskbar.
Figure 4.48 - Safely
Remove Hardware Icon
You can learn more about device drivers in the A+ TWO course.
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Stopping a device is especially
important when the device
being removed is a storage
device, such as a hard disk
drive. Not stopping the device
may prevent data in RAM
from being written to the disk
leading to data loss and
corruption.
Double-clicking the Safely
Remove Hardware icon will
display a dialogue box, from
which you may select the
devices that you wish to stop.
Figure 4.49 - Safely Remove Hardware
Dialogue
Stopping the device will inform all processes that are running on the
computer that the device is about to be removed. If this action may
lead to loss or corruption of data, a warning message will be displayed
on the screen.
Figure 4.50 - Safely Remove Hardware Warning Message
Knowledge Check
4.1
What sort of USB connector is found on a hub?
What is the official maximum length of one USB cable?
How much power can one USB port provide?
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Summary
ISA, AGP and PCI are buses that provide expansion slots on the
motherboard for plugging in interface cards. Devices may then be
connected to the interface cards. For example, a sound card can be
connected to a PCI bus expansion slot, and a microphone and
speakers attached to the sound card. In contrast, USB is a bus that
provides ports, which are part of a USB hub, for connecting devices.
Each USB bus begins with a host controller. The host controller may
be built into the motherboard or it may be an add-on interface card.
The host controller provides a root hub with one or more A ports.
USB devices have a B or mini-B port built into them. Devices connect
to a USB hub using a cable with an A plug at one end and a B or
mini-B plug at the other. Large devices such as printers and scanners
use B ports. Small devices such as cameras and external drives use
mini-B ports.
To provide more A ports for connecting more devices, external USB
hubs can be cascaded from the root hub, and from each other.
USB can provide power to the devices plugged into it, although some
devices, especially printers and scanners, will need to be plugged into
the mains electrical supply.
A USB bus can support a total of 127 devices.
IEEE 1394 – FireWire
The IEEE 1394 bus is referred to as i.Link by Sony, FireWire by Apple
and most PC manufacturers, and very rarely as HPSB (High
Performance Serial Bus).
FireWire is not as prevalent as USB, even though it has been an official
standard since December 1995. It is not built into as many
motherboards as USB and therefore may require the addition of a
FireWire interface card.
Although not as widespread as USB, the participation of large
corporations such as Microsoft, Apple, Sony and Adaptec in the 1394
Trade Association (which develops the standard) indicates that FireWire
may be around for some time.
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Available FireWire devices include digital cameras, camcorders,
CD/DVD writers, hard disk drives and tape backup devices.
There are two versions of
FireWire – FireWire 400 (IEEE
1394a), which has a transfer
rate of 400 Mbps and
FireWire 800 (IEEE 1394b),
which has a transfer rate of
800 Mbps. FireWire 800
devices require cables and
ports with a special 9-pin
connection.
Figure 4.51 - FireWire 400 and 800 Logos
The structure of FireWire is basically the same as USB. The start of a
FireWire bus is a host controller. Built into the host controller will be
one or more ports in a root hub.
Figure 4.52 - Firewire Host Controller Built into Motherboard
Devices are connected to the ports on the host controller in a
hierarchical tree topology (similar to USB).
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FireWire Connectors and Cables
Figure 4.53 - 6-pin (left) and 4-pin
FireWire Plugs
Figure 4.54 – 9-pin FireWire Plug
FireWire 400 cables have either 6-pin or 4-pin connectors; there is also
a 9-pin connector used by FireWire 800. FireWire devices connect
together using a similar structure to USB; they use male connectors at
each end of a cable, which links directly to a port on the motherboard,
interface card or hub.
The original 6-pin FireWire connectors are found on PCs, hubs and
hard drives; 4-pin connectors are standard on AV equipment such as
camcorders. Cables and converters are available that allow 4-pin
devices to connect to a 6-pin port and vice-versa.
Figure 4.55 – 4-pin FireWire Port
Figure 4.56 - 6-pin FireWire Port
FireWire 400 can connect up to 63 devices, using cables up to 4.5
metres long and with a maximum bus length of 72 metres. FireWire
800 increases the maximum distance of transmission to 100 metres
using optical fibre cables.
In addition to its high speed, FireWire is also capable of delivering data
at a guaranteed rate, known as isochronous communications. This
makes it ideal for devices that need to transfer a large amount of data in
real-time, such as video cameras.
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FireWire Power
FireWire can provide power (between 8 and 30 volts, 1.5 amps
maximum) to attached peripherals. As with USB, if this is insufficient,
the peripheral will have to be connected to the mains electrical supply.
FireWire does not provide any power to devices using 4-pin cables and
connectors; this must have their own power supply.
Installing FireWire Devices
The procedures for the installation and removal of FireWire devices are
the same as for USB devices.
Summary
FireWire is similar to USB in that it uses hubs and cables to connect
devices to FireWire ports in the PC; however USB devices cannot
plug into a FireWire port and vice-versa.
FireWire supports fewer total devices per bus than USB (63 as
compared to 127), however the total bus length can be longer (72100 metres as compared to 30 metres), and FireWire 800 supports a
faster data transfer rate than USB 2.0 (800 Mbps as compared to 480
Mbps).
The table below summarises the differences between USB and
FireWire.
Table 4.3 - USB - FireWire Comparison
Version
Max bandwidth
Max bus length
Max cable length
Max devices
USB
1.1
2.0
12 Mbps
480 Mbps
30 metres
5 metres
127
FireWire
400
800
400 Mbps
800 Mbps
72 metres
100 metres
4.5 metres
63
Specialised slots
In order to be sold in the USA, any equipment that may cause harmful
emissions is required to obtain FCC certification; this includes PC
devices such as audio, modem and network interfaces.
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This means that any new motherboard with integrated sound, audio or
network interface built into them has to undergo an FCC certification
process.
Manufacturers realised that they could save costs by creating an audio,
modem or network interface card (or a card with any combination of
these functions) which passed FCC certification. They could then use
this card in new motherboards, allowing them to skip the certification
process for the motherboard itself.
Designing a dedicated type of bus slot for these cards rather than
plugging them into a standard slot provided further flexibility. Even if
other bus technologies changed, the sound/modem/network card could
remain the same; all that would need to change is the interface between
the new bus technology and the specialised slot.
Three examples of these types of specialised slots exist: AMR, CNR and
ACR.
AMR (Audio Modem Riser)
AMR was introduced by Intel in
1998. The AMR (Audio Modem
Riser) standard specifies that one of
the available PCI slots on the
motherboard is replaced with an
AMR slot.
Figure 4.57 - AMR Slot
AMR riser cards provide access to a telephone modem (V.92 standard),
a microphone socket, and line in/line out sockets for speakers etc.
CNR (Communication Networking Riser)
CNR is another Intel standard which
replaced AMR. A CNR card is not
limited to audio and standard
telephone modem functions, as AMR
is. CNR supports other technology
such as ADSL and Ethernet
networking. Unlike AMR, CNR is
Plug and Play capable.
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Figure 4.58 - CNR Slot (at Edge of
Motherboard)
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ACR (Advanced Communications Riser)
ACR is a standard defined by a consortium of companies as a rival to
Intel’s CNR. It provides access to the same technologies as AMR but
offers improvements in terms of speed and efficiency.
An ACR slot is located at the edge of the motherboard and looks like a
3.3V PCI slot; it is set slightly nearer to the edge of the motherboard
than the PCI slots. In the figure below the ACR slot is at the bottom,
below the PCI slots.
Figure 4.59 - ACR Slot (bottom)
All of these technologies have been rendered virtually obsolete; with
manufacturers preferring to build audio/modem/network etc
functionality directly into the motherboard.
Memory Slots
PC memory is discussed as a separate topic in a later module of this
course; here we will just briefly describe the types of memory slots that
are found on motherboards.
SIMM slots
SIMM slots are only found on very old systems, such as 80386, 80486
and original Pentium CPU motherboards. They are briefly described
here purely as a matter of historical interest; they are too old to appear
in the A+ exam.
There are two types of SIMM slot; 30-pin and 72-pin. Both type of slot
can transfer 32-bits at a time.
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Obviously, 30-pin SIMM slots contain 30 pins, or electrical connectors,
but if you counted the pins in a 30-pin SIMM slot, or on a 30-pin SIMM
card, you would actually find 60 of them; 30 per side. The reason these
slots and cards are called 30-pin is because each side of connectors
actually carry the same signal. In other words; one set of 30-pins is
redundant.
30-pin SIMM slots would only be found on 80386 and 80486
CPU-based motherboards.
Figure 4.60 - 30-pin SIMM slots
72-pin SIMM slots also have a redundant side of connectors, so there
are in fact 144-pins in a 72-pin slot and the edges of a 72-pin SIMM
card.
72-pin SIMM slots would only be found on 80486 and original Pentium
CPU-based motherboards.
Figure 4.61 - 72-pin SIMM slots
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DIMM slots
DIMMs are used in modern Pentium motherboards. There are three
main types; 168-pin, 184-pin and 240-pin.
Unlike SIMMs, the contacts on each side of a DIMM slot/card carry
different signals, so each side of a 168-pin DIMM slot has 84 connectors
and so on; also DIMMs transfer 64-bits at a time.
Figure 4.62 - DIMM slots
CPU Sockets
Processors are usually housed on the motherboard in either a socket or
a slot; this allows them to be easily upgraded, or replaced if they are
faulty.
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Although CPUs are usually housed in a
socket or slot on the motherboard,
sometimes they are soldered (hardwired) on. An example of this is
shown on the right. This is a nano-ITX
motherboard, and it is not much bigger
than a CD-ROM case. The CPU –
which is the small, lightly-coloured
square chip at the centre of the top
edge of the motherboard – is a VIA
Technologies Eden CPU.
Figure 4.63 - Nano-ITX
CPU Sockets
Sockets can be categorised as PGA, SPGA or LGA. A PGA (Pin Grid
Array) socket has a symmetrical layout of holes and is the format used
by older CPUs such as the 80486. An SPGA (Staggered Pin Grid Array)
socket has an arrangement where each row of holes is offset from the
row next to it. This allows pins to be packed more densely. An LGA
(Land Grid Array) socket has the pins in the socket rather than the CPU.
Instead, the CPU has metal pads which make contact with the pins in
the socket.
Sockets may also be categorized as LIF (Low Insertion Force) or ZIF
(Zero Insertion Force).
A LIF socket has holes for the CPU pins that provide a tight and precise
fit. Care is needed when inserting and removing chips, in order to
avoid damaging the pins. The tight fit and the large number of pins
means that considerable force sometimes needs to be used, increasing
the possibility of damage. 80286, 80386 and 80486 CPUs use LIF
sockets.
A ZIF socket incorporates a lever. When the lever is raised, there is a
loose fit between pins and the corresponding holes in the socket. The
chip can be dropped into place. When the lever is lowered, the pins
are clamped tightly into position. Pentium CPUs use ZIF sockets.
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Figure 4.64 – PGA
(LIF)
Module 4: Motherboards
Figure 4.65 – SPGA
(ZIF)
Figure 4.66 – LGA (ZIF)
CPU Slots
A CPU slot is similar in appearance to an expansion bus slot. It uses a
set of edge connectors to make contact with the processor rather than a
pin/hole arrangement.
Figure 4.67 – Slot 1
CPU/Socket Reference Table
The type of CPU socket or slot a motherboard has, will determine what
CPU replacements or upgrades are possible.
You will need to be able to identify which CPU fits into which
socket/slot, for most of the current Intel and AMD processors.
There now follows a set of reference tables listing the sockets and slots
used by Intel and AMD CPUs. There is a lot of information here, and it
would be unreasonable to expect you to remember it all.
However, you should at least familiarise yourself with which general
class of CPU fits into which socket. For example, you should know that
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Socket 370 is used by Pentium III and Pentium III Celeron CPUs, and
Socket 775 is used by Pentium 4 CPUs.
Always refer to your motherboard documentation to find out exactly
which CPUs are compatible with it.
Table 4.4 - CPU/Socket reference
Socket name
Socket 4
Socket 5
Socket 6
Socket 7
Super Socket 7
Socket 8
Slot 1
Slot 2
Slot A
Socket 370
Socket 462/
Socket A
Socket 423
Socket 478/
Socket N
Socket 495
Socket 603
Socket 604
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CPU families
Intel Pentium
Intel Pentium
AMD K5
Intel 80486
Intel Pentium
Intel Pentium MMX
AMD K6
AMD K6-2
AMD AMD K6-III
Cyrix MII
Intel Pentium Pro
Intel Pentium II
Intel Pentium III
Intel Pentium II Xeon
AMD Athlon
Intel Pentium III
Intel Celeron
AMD Athlon
AMD Duron
AMD Athlon XP
AMD Athlon XP-M
AMD Athlon MP
AMD Sempron
Intel Pentium 4
Intel Pentium 4
Intel Celeron
Intel Pentium 4 EE
Intel Pentium M
Intel Celeron
Intel Xeon
Intel Xeon
Package
PGA
PGA
8003-0100–SM–T
© 2009 N+S training!
PGA
PGA
PGA
PGA
Slot
Slot
Slot
PGA
PGA
PGA
PGA
PGA
PGA
PGA
A+ Certification - ONE
Socket name
Socket 754
Socket 940
Socket 479
Socket 939
LGA 775/
Socket T
Socket 563
Socket M
LGA 771/
Socket J
Socket S1
Socket AM2
Socket F
Socket AM2+
Socket P
Socket 441
© 2009 N+S training!
Module 4: Motherboards
CPU families
AMD Athlon 64
AMD Sempron
AMD Turion 64
AMD Opteron Athlon 64 FX
Intel Pentium M
Intel Celeron M
Intel Core Duo
Intel Core Solo
AMD Athlon 64
AMD Athlon 64 FX
AMD Athlon 64 X2
AMD Opteron
Intel Pentium 4
Intel Pentium D
Intel Celeron
Intel Celeron D
Intel Pentium XE
Intel Core 2 Duo
Intel Core 2 Quad
Intel Xeon
AMD Athlon XP-M
Intel Core Solo
Intel Core Duo
Intel Dual-Core Xeon
Intel Core 2 Duo
Intel Xeon
Package
PGA
AMD Turion 64 X2
AMD Athlon 64
AMD Athlon 64 X2
AMD Athlon 64 FX
AMD Opteron
AMD Athlon 64
AMD Athlon X2
AMD Phenom
Intel Core 2
Intel Atom
PGA
PGA
8003-0100–SM–T
PGA
PGA
PGA
LGA
PGA
PGA
LGA
LGA
PGA
PGA
PGA
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Socket name
LGA 1366/
Socket B
Socket AM3
Socket 1155
LGA 1156/
Socket H
Socket 1567
Module 4: Motherboards
CPU families
Intel Core i7
Intel Core i9
AMD Phenom II
AMD Athlon II
Intel Core i5
Intel Core i3
Intel Core i5
Intel Core i7
Intel Xeon
Package
LGA
PGA
LGA
LGA
LGA
Installing and Configuring a Motherboard
As long as they are not physically damaged or used under inappropriate
operating conditions (eg extremely high ambient temperatures)
motherboards are not prone to frequent failure.
PC upgrades typically involve devices that will directly increase
performance, capacity or functionality, such as increasing system RAM,
adding a hard disk drive, or installing a TV tuner card.
For the reasons listed above, motherboard installations are most often
performed when building a PC from individually purchased
components.
Connecting the Motherboard
After attaching the PSU to the system case, connecting the motherboard
is often the first task carried out when building a PC.
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Module 4: Motherboards
When carrying out
any hardware
installation it is wise
to prepare carefully;
installing a
motherboard is no
exception.
First, you should
unpack your
motherboard and
use the packing
contents sheet to
ensure that no parts
are missing.
Figure 4.68 - Typical Motherboard Box Contents
A new motherboard is normally accompanied by some or all of the
following items:
User / Installation Manual
Driver CD or DVD
Rear I/O plate
SATA cable(s)
PATA cable(s)
Floppy cable
Mounting Screws
Stand-offs
Next you should test fit your motherboard in the system case to
determine which mounting points (screw holes) you are going to use,
and whether you will use the system case’s pre-fitted I/O plate or the
one supplied with the motherboard.
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Module 4: Motherboards
Figure 4.69 – Test-fitting a motherboard
If you have the optional CD that accompanies this book, you can see
this process in more detail by watching the motherboard installation
videos.
If required, snap off the system case’s I/O plate and push in the one
supplied with the motherboard and install any stand-offs that you need
to, then screw the motherboard to the system case.
Attaching Cables
With the motherboard now secured to the system case you can start to
attach the initial cables to it. These include the following.
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Module 4: Motherboards
Main power connector
Depending on the form factor of your motherboard and PSU, the main
power connector will have 20- or 24-pins.
The shape of the connector makes it impossible to attach it incorrectly.
Do make sure though that the connector is firmly attached to the
motherboard.
Secondary power connector
Again, depending on the form factor of your motherboard and PSU,
there may be a secondary power connector such as a 4-pin P4
connector used by ATX12V motherboards / PSUs.
Make sure that this connector is also firmly attached.
System fan power connector
If your system case provides its own fan, often referred to as a system
fan, the motherboard should provide a connector for this.
Front panel switches / LEDs
The front panel of your system case should provide some or all of the
following: an On/Off switch; a power reset switch;, LED indicators for
drive activity and power; a speaker. Behind these switches there will be
cables which must be connected to the motherboard.
There is no universal system of marking for where these cables connect
to on your motherboard; you will have to rely on the quality of your
motherboard’s documentation.
A typical example is shown in Figure 4.70:
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Module 4: Motherboards
Figure 4.70 - Motherboard front panel connectors diagram
The front panel may also provide I/O ports such as USB, FireWire,
eSATA (external SATA) and audio, as with the On/Off switches etc,
there will be cables behind these I/O ports which connect to the
motherboard. In your motherboard manual you should find what are
referred to as headers for these cables as in Figure 4.71:
Figure 4.71 - Motherboard USB header diagram
Once all cables have been connected, you should next install your CPU
and memory. Installation of CPUs and memory is covered in later
modules.
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Module 4: Motherboards
You should now connect a monitor and keyboard to the motherboard,
and then plug the PSU into the mains. You are now in a position to
boot up for the first time. At this very early stage of a PC build you will
not be in a position to run an operating system such as Windows, as
you have not even connected a hard disk drive to your PC, let alone
performed the operating system installation. You should however be
able to test that your motherboard is functioning.
BIOS / NVRAM Settings
Once you have performed the motherboard/CPU/memory installation
described above, you should be able to run the BIOS setup utility to test
that your motherboard is functioning, and to configure any motherboard
settings that you want to.
Switch on the PC and watch the monitor closely. It should tell you
which key to press on the keyboard to invoke the BIOS setup utility.
You motherboard manual should also tell you this information. The key
will most likely be Del, Esc, or an F (function) key such as F1 or F2.
Use the BIOS setup utility to check the following.
Your date and time are set correctly (although this is not of
major importance as it can be set later using Windows once it
has been installed).
You have set appropriate security (it is worthwhile password
protecting at least your BIOS setup utility to prevent incorrect /
unauthorized user tampering)
The boot device sequence is set up appropriately (check that
the optical drive is before the hard drive in the sequence; this
will ease the process of booting from a CD/DVD in an
emergency, ie when the hard drive has failed.)
You are now ready to start attaching your drives and any other devices;
once this has been done you can commence your operating system
installation.
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Review
The original IBM PC used an AT motherboard form factor. This has
been replaced by ATX and BTX as the most common form factors used
in standard desktop PCs. There is a specialised motherboard form factor
called ITX which is used for building small footprint PCs; ITX is used
quite widely by those who build gaming PCs.
A chipset controls traffic flow between the PC’s components. Most
chipsets are divided into a Northbridge (Memory Controller Hub) and
Southbridge (I/O Controller Hub). Northbridge controls communication
between the CPU, memory and the AGP or PCIe video bus.
Southbridge controls all other communication.
All motherboards have a flash ROM chip which is called the BIOS chip.
The BIOS chip contains the POST, a bootstrap programme, hardware
access routines and a setup programme. Updating the contents of a
BIOS chip is called flashing the BIOS. BIOS chips are flashed by
running a programme that has usually been downloaded from the
manufacturer’s web site.
To run the BIOS setup programme, a keyboard key is pressed during
boot up. This key is usually Del, Esc or a function key. The BIOS setup
programme can be used to change the date and time, set power-on
passwords, alter clock speeds, and alter CPU settings. Settings created
by the setup programme are stored in NVRAM. NVRAM settings can
usually be cleared by a jumper on the motherboard.
A typical motherboard will provide slots for adding cards, such as a TV
tuner card or a video card. These slots may be PCI, PCI-X or PCIe slots.
There may also be an AGP slot for a video card. Common peripheral
devices, such as printers and scanners, connect to a USB or FireWire
bus.
AMR, CNR, and ACR slots, sometimes referred to a riser card slots, are
sometimes used by computer manufacturers for audio/modem/network
cards.
System RAM is provided in the form of specialised cards called memory
modules. Older motherboards used SIMMs, modern motherboards use
DIMMs.
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Module 4: Motherboards
CPUs are fitted into a socket on the motherboard. The layout of these
sockets may be PGA, SPGA or LGA. The quick-release mechanism
provided by these sockets is called ZIF.
Installing a new motherboard requires that you:
Fit the motherboard to the system case;
Cover the rear ports (PS2, USB, video etc) with an I/O plate;
Attach the power cables;
Attach the front panel switch and LED cables;
Configure NVRAM settings using the BIOS setup programme.
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Review Questions
1
Which motherboard form factor is used in low-profile systems
cases?
2
A chipset is normally divided into two parts. What are these parts
called?
3
What type of ROM are modern BIOS chips made from?
4
A PC is producing a series of beeps as it powers up. What
programme is producing these beeps?
5
You want to set up your PC so that it always searches your optical
drive first for an operating system. Which programme would you
run to make this setting?
e
6
The setting that you created in the previous question would be
saved where?
7
Which type of bus slot may contain only a video card?
8
What should you do before removing an external USB hard disk
drive?
.
9
Your video camera supports both USB and FireWire connectivity.
Which of them should you use for streaming live video from your
video camera to the computer?
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10
Module 4: Motherboards
Which Intel CPUs are compatible with an LGA 1156 socket?
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