7
Understanding Motherboards
“Man is most nearly himself
when he achieves the seriousness
of a child at play.”
—HERACLITUS, CIRCA 500 B.C.
In this chapter, you will learn
how to
T
he motherboard provides the foundation for the personal computer.
Every piece of hardware, from the CPU to the lowliest expansion card,
■
Explain how motherboards work
■
Identify the types of
motherboards
wires—called traces —that make up the different buses of the system. It holds
Explain chipset varieties
the vast majority of the ports used by the peripherals and it distributes the
■
directly or indirectly plugs into the motherboard. The motherboard contains the
power from the power supply (Figure 7.1). Without the motherboard, you
literally have no PC.
168
Historical/Conceptual
■
How Motherboards Work
Three variable and interrelated characteristics define modern motherboards: form factor, chipset, and components. The form factor determines
the physical size of the motherboard as well as the general location of components and ports. The chipset defines the type of processor and RAM required for the motherboard, and determines to a degree the built-in devices
supported by a motherboard, including the expansion slots. Finally, the
built-in components determine the core functionality of the system.
Any good tech should be able to make a recommendation to a client
about a particular motherboard simply by perusing the specs. Because the
motherboard determines function, expansion, and stability for the whole
PC, it’s essential that you know your motherboards!
Form Factors
Form factors are industry standardized shapes and layouts that enable
motherboards to work with cases and power supplies. A single form factor
applies to all three components. All motherboards come in a basic rectangular or square shape, for example, but vary in overall size and the layout of
built-in components (Figure 7.2). You need to install a motherboard in a case
designed to fit it, so the ports and slot openings on the back fit correctly.
• Figure 7.1
Tech Tip
Layers of the PCB
Modern motherboards—officially
printed circuit boards (PCBs)—
come in multiple layers and thus
mask some of their complexity.
You can see some of the traces on
the board, but every motherboard
is two or more layers thick.
There’s a veritable highway of
wires in the layers, carrying data
and commands back and forth between CPU, Northbridge, RAM,
and peripherals. The layered
structure enables multiple wires
to send data without their signals
interfering with each other. The
layered approach allows the manufacturer to add complexity and
additional components to the
board without having to extend
the overall length and width of
the board. Shorter traces also allow signals to travel faster than
they would if the wires were longer, as would be necessary if
motherboards did not use layers.
The multiple layers also add
strength to the board itself,
helping prevent it from bending
when used.
Traces visible beneath the CPU socket on a motherboard
Chapter 7: Understanding Motherboards
169
• Figure 7.2
The power supply and the motherboard need matching connectors,
and different form factors define different connections. Given that the
term “form factor” applies to the
case, motherboard, and power supply⎯the three parts of the PC most
responsible for moving air around
inside the PC—the form factor also
defines how the air moves around in
the case.
To perform motherboard upgrades and provide knowledgeable
recommendations to clients, techs
need to know their form factors.
The PC industry has adopted⎯and
dropped⎯a number of form factors
over the years with names such as
AT, ATX, BTX, and others. Let’s
start with the granddaddy of all PC
form factors, AT.
Typical motherboard
AT Form Factor
The AT form factor (Figure 7.3), invented by IBM in the early 1980s, was the
predominant form factor for motherboards through the mid-1990s. AT is
now obsolete. The AT type of motherboard had a large keyboard plug in the
same relative spot on the motherboard, and it had a unique, split power
socket called P8/P9 .
The AT motherboard had a few size variations, ranging from large to very
large (Figure 7.4). The original AT motherboard was huge, around 12 inches
wide by 13 inches deep. PC technology was new and needed a lot of
space for the various chips necessary
to run the components of the PC,
such as the keyboard.
The single greatest problem
with AT motherboards was the lack
of external ports. When PCs were
first invented, the only devices
plugged into the average PC were a
monitor and a keyboard. That’s
what the AT was designed to handle—the only dedicated connector
on an AT motherboard was the keyboard plug (Figure 7.5).
Over the years, the number of
devices plugged into the back of the
PC has grown tremendously. Your
average PC today has a keyboard,
• Figure 7.3
170
AT-style motherboard
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
• Figure 7.4
AT motherboard (bottom) and Baby AT motherboard (top)
a mouse, a printer, some speakers, a monitor, and if your system’s like mine,
four to six USB devices connected to it at any given time. These added components created a demand for a new type of form factor, one with more dedicated connectors for more devices. Many attempts were made to create a
new standard form factor. Invariably, these new form factors integrated
dedicated connectors for at least the mouse and printer, and many even
added connectors for video, sound, and phone lines.
One variation from the AT form factor that enjoyed a degree of success
was the slimline form factor. The first slimline form factor was known as
LPX (defined in some sources as low profile extended, although there’s some
disagreement). It was replaced by the NLX form factor. (NLX apparently
stands for nothing, by the way. It’s just a cool grouping of letters.) The LPX
and NLX form factors met the demands of the slimline market by
providing a central riser slot to enable the insertion of a special riser
card (Figure 7.6). Expansion cards
then fit into the riser card horizontally. Combining built-in connections with a riser card enabled
manufacturers to produce PCs
shorter than 4 inches.
The main problem with form
factors like LPX and NLX was their
inflexibility. Certainly, no problem
occurred with dedicated connections for devices such as mice or
printers, but the new form factors
also added connectors for devices
like video and sound—devices that • Figure 7.5 Keyboard connector on the back of an AT motherboard
Chapter 7: Understanding Motherboards
171
• Figure 7.6
Riser card on an older motherboard
were prone to obsolescence, making the motherboard out of date the moment a new type of video or sound card came into popularity.
Essentials
ATX Form Factor
Tech Tip
There continued to be a tremendous demand for a new form factor—a form
factor that had more standard connectors, but at the same time was flexible
enough for possible changes in technology. This demand led to the creation
of the ATX form factor in 1995 (Figure 7.7). ATX got off to a slow start, but by
around 1998 ATX overtook AT to become the most common form factor
used today.
Soft Power
ATX motherboards use a feature
called soft power. This means
that they can use software to turn
the PC on and off. The physical
manifestation of soft power is the
power switch. Instead of the thick
power cord used in AT systems,
an ATX power switch is little
more than a pair of small wires
leading to the motherboard. We
delve into this in more detail in
Chapter 8, “Understanding
PC Power.”
172
Cross Check
High-Speed CPUs and RAM
With the newly shortened wire lengths between CPU, Northbridge, and
RAM, manufacturers could crank up at least that part of the motherboard
speed. CPU and RAM manufacturers quickly took advantage of the new
speed potential. Refer to Chapters 3 and 4, on “Understanding CPUs”
and “Understanding RAM,” respectively, and see if you can answer
these questions.
1.
Which CPUs can take advantage of such speed increases?
2.
What type(s) of RAM can you put in those same systems to
optimize the flow of data to the CPU?
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
CPU in socket
AGP slot
External ports
CPU fan power
RAM
PCI slots
Northbridge
Flash BIOS chip
System clock battery
Front panel
connections
Power connector
Southbridge
DIP switches
• Figure 7.7
Floppy port
EIDE ports
Early ATX motherboard
ATX is distinct from AT in the lack of an AT keyboard port, replaced
with a rear panel that has all necessary ports built in. Note the mini-DIN
(PS/2) keyboard and mouse ports in Figure 7.8, standard features on almost
all ATX boards.
The ATX form factor includes many improvements over AT. The position
of the power supply enables better air movement. The CPU and RAM are
placed to enable easier access. Other improvements, such as placement of
RAM closer to the Northbridge and CPU than on AT boards, offer users enhanced performance as well. The shorter the wires, the easier to shield them
and make them capable of handling double or quadruple the clock speed of
Parallel port
Joystick/MIDI port
PS/2 (mouse)
PS/2 (keyboard)
USB ports
• Figure 7.8
Serial ports
Mini-audio ports (speaker, line-in, microphone)
ATX ports
Chapter 7: Understanding Motherboards
173
• Figure 7.9
AT (left) and ATX (right) motherboards for quick visual comparison
You’ll find many techs and
Web sites use the term miniATX to refer to motherboards
smaller than a full ATX board.
This is technically incorrect. The
specifications for these small
boards use only the terms
microATX and FlexATX.
• Figure 7.10
174
MicroATX
the motherboard. Figure 7.9 shows an AT and an ATX motherboard—note
the radical differences in placement of internal connections.
The success of ATX has spawned two form factor subtypes for specialty
uses. The microATX motherboard (Figure 7.10) floats in at a svelte 9.6 by
9.6 inches or about 30 percent smaller than standard ATX, yet still uses the
standard ATX connections. A microATX motherboard fits into a standard
ATX case or in the much smaller microATX cases. Note that not all
microATX motherboards have the same physical size. You’ll sometimes see
microATX motherboards referred to with the Greek
symbol for micro, as in μATX.
In 1999, Intel created a variant of the microATX
called the FlexATX. FlexATX motherboards have
maximum dimensions of just 9 by 7.5 inches, which
makes them the smallest motherboards in the ATX
standard. Although FlexATX motherboards can use
a standard ATX power supply, most FlexATX systems use a special FlexATX-only power supply. This
diminutive power supply fits into tight FlexATX
cases.
Keep in mind that each main type of form factor
requires its own case. AT motherboards go into AT
cases, NLX motherboards go into NLX cases, and
ATX motherboards go into ATX cases. You cannot
replace one form factor with another without purchasing a new case (Figure 7.11). The exception to
this rule is that larger form factor ATX cases can handle any smaller-sized form factor motherboards.
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
BTX Form Factor
Even though ATX addressed ventilation, faster CPUs and powerful graphics
cards create phenomenal amounts of
heat, motivating the PC industry to create the “coolest” new form factor used
today⎯the Balanced Technology eXtended (BTX) form factor (Figure 7.12).
BTX defines three subtypes: standard
BTX, microBTX , and picoBTX , designed to replace ATX, microATX, and
FlexATX, respectively.
At first glance, BTX looks like ATX,
but notice that the I/O ports and the expansion slots have switched sides. You
can’t put a BTX motherboard in an ATX
case! BTX does not change the power
connection, so there’s no such thing as a
BTX power supply.
Everything in the BTX form factor is
designed to improve cooling. BTX cases • Figure 7.11 That’s not going to fit!
vent in cool air from the front and warm
air out the back. CPUs are moved to the
front of the motherboard so they get cool air coming in from the front of the
case. BTX defines a special heat sink and fan assembly called the thermal
unit . The thermal unit’s fan blows the hot CPU air directly out the back of
the case, as opposed to the ATX method of just blowing the air into the case.
• Figure 7.12
Many manufacturers sell
what they call “BTX power supplies.” These are actually marketing gimmicks. See Chapter 8,
“Understanding PC Power,” for
details.
microBTX motherboard
Chapter 7: Understanding Motherboards
175
Try This!
Motherboard Varieties
Motherboards come in a wide variety of form factors. Go to your local
computer store and check out what is on display. Note the different features offered by ATX, microATX, and FlexATX (if any) motherboards.
1.
Does the store still stock any AT motherboards?
2.
What about NLX, BTX, or proprietary motherboards?
3.
Did the clerk use tech slang and call the motherboards “mobos”?
(It’s what most of us call them outside of formal textbooks,
after all!)
The BTX standard is clearly a
much cooler option than ATX, but
the PC industry tends to take its
time when making big changes
like moving to a new form factor.
As a result, BTX has not yet made
much of an impact in the industry,
and BTX motherboards, cases, and
thermal units are still fairly rare.
BTX could take off to become the
next big thing or disappear in a
cloud of disinterest⎯only time
will tell.
Proprietary Form Factors
Several major PC makers, including Dell and Sony, make motherboards that
work only with their cases. These proprietary motherboards enable these
companies to create systems that stand out from the generic ones and, not
coincidently, push you to get service and upgrades from their authorized
dealers. Some of the features you’ll see in proprietary systems are riser
boards like you see with the NLX form factor—part of a motherboard separate from the main one, but connected by a cable of some sort—and unique
power connections. Proprietary motherboards drive techs crazy as replacement parts tend to cost more and are not readily available.
Chipset
• Figure 7.13
176
Northbridge (under the fan) and Southbridge (lower right, labeled VIA)
Every motherboard has a chipset. The
chipset determines the type of processor
the motherboard accepts, the type and
capacity of RAM, and what sort of internal and external devices the motherboard supports. As you learned in
earlier chapters, the chips in a PC’s
chipset serve as electronic interfaces
through which the CPU, RAM, and input/output devices interact. Chipsets
vary in feature, performance, and stability, so they factor hugely in the purchase or recommendation of a particular
motherboard. Good techs know their
chipsets!
Because the chipset facilitates communication between the CPU and other
devices in the system, its component
chips are relatively centrally located on
the motherboard (Figure 7.13). Most
modern chipsets are composed of two
primary chips—the Northbridge and
the Southbridge.
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
The Northbridge chip on Intel-based motherboards helps the CPU work with RAM, as mentioned in earlier chapters. On AMD-based
motherboards, the Northbridge provides the
communication with the video card, rather than
memory, because the memory controller is built
into the CPU. Current Northbridge chips do a lot
and thus get pretty hot, so they get their own heat
sink and fan assembly (Figure 7.14).
The Southbridge handles some expansion
devices and mass storage drives, such as hard
drives. Most Southbridge chips don’t need extra
cooling, leaving the chip exposed or passively
cooled with only a heat sink. This makes the
Southbridge a great place to see the manufacturer of the chipset, such as Intel (Figure 7.15).
Most motherboards support very old technologies such as floppy drives, infrared con- • Figure 7.14 Heat sink and fan on a Northbridge
nections, parallel ports, and modems.
Although supporting these old devices was
once part of the Southbridge’s job, hardly any modern chipsets still support
these devices. Motherboard manufacturers add a third chip called the Super
Super I/O chips work with
chipsets but are not part of the
I/O chip to handle these chores. Figure 7.16 shows a typical Super I/O chip.
chipset. Motherboard makers
The system ROM chip provides part of the BIOS for the chipset, but only
purchase them separately from
a barebones, generic level of support. The chipset still needs support for the
chipsets.
rest of the things it can do. So, how do expansion devices get BIOS? Software
drivers, of course, and the same holds true for modern chipsets. You have to
load the proper drivers for the specific OS to support all the features of today’s chipsets. Without software drivers, you’ll never create a stable, fully
functional PC. All motherboards ship with a CD-ROM disc with drivers,
• Figure 7.15
An Intel NH82801 Southbridge chip on a motherboard
Chapter 7: Understanding Motherboards
177
support programs, and extra special goodies such as anti-virus software (Figure 7.17).
There are a limited number of
chipset makers. Both AMD and
Intel make chipsets, but although
they may control the CPU market,
they have some serious competition
in the chipset market. Two
third-party chipset makers, VIA
Technologies and NVIDIA Corporation , make some very popular
chipsets. Motherboard manufacturers incorporate the chipsets into
motherboards that match the fea• Figure 7.16 Super I/O chip on ASUS motherboard
ture set of the chipset. Some of the
companies produce chipsets designed for both Intel and AMD
Tech Tip
CPUs, whereas others choose one
or the other company to support. Chipset companies rise and fall every few
AMD and ATI
years, with one company seeming to hold the hot position for a while until
Due to the purchase by AMD of
another company comes along to unseat them.
chipset (and video card) maker
Chipset makers don’t always use the terms Northbridge and
ATI in 2006, the chipset field has
Southbridge. Chipsets for AMD-based motherboards tend to use the terms,
the potential to change again.
but Intel-based motherboards prefer to use the terms Memory Controller
ATI makes a nice line of mobile
Hub (MCH) for the Northbridge and I/O Controller Hub (ICH) for the
and desktop chipsets. Backed by
Southbridge. Regardless of the official name, Northbridge and Southbridge
AMD’s muscle, the combined
are the commonly used terms. Figure 7.18 shows a schematic with typical
companies might give VIA and
chipset chores for a VIA K8T900 chipset.
NVIDIA a run for their money.
Only time will tell, but it’s someIt would be impossible to provide an inclusive chipset chart here
thing for informed CompTIA A+
that wouldn’t be obsolete by the time you pick this book up off the shelf at
certified techs to watch.
In an average year, chipset
makers collectively produce
around one hundred new chipset
models for the PC market.
• Figure 7.17
178
Driver disc for ASUS motherboard
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
your local tech pub (doesn’t everybody have one of those?), but
Table 7.1 gives you an idea of what
to look for as you research motherboards for recommendations and
purchases.
So why do good techs need to
know the hot chipsets in detail?
The chipset defines almost every
motherboard feature short of the
CPU itself. Techs love to discuss
chipsets and expect a fellow tech
to know the differences between
one chipset and another. You also
need to be able to recommend a
motherboard that suits a client’s
needs.
Try This!
VIA Makes What?
The giant Taiwan-based VIA Technologies produces many chips for
many different markets and competes directly with Intel on several levels. Some of these might surprise you. Try this: go to VIA’s Web site
(www.via.com.tw) and see if you can answer the following questions.
1.
VIA chipsets support which CPUs?
2.
What technological innovations does VIA push? What about
form factors?
3.
Does VIA produce processing chips of the non-chipset variety,
such as for video, sound, or general computing? What are they
called?
Motherboard
Components
The connections and capabilities of
a motherboard sometimes differ
from that of the chipset the motherboard uses. This disparity happens
for a couple of reasons. First, a particular chipset may support eight
USB ports, but to keep costs down
the manufacturer might include
only four ports. Second, a motherboard maker may choose to install
extra features⎯ones not supported
by the chipset⎯by adding additional chips. A common example is
a motherboard that supports
FireWire. Other technologies you
might find are built-in sound, hard
drive RAID controllers, and AMR
or CNR slots for modems, network
cards, and more.
USB/FireWire
Most chipsets support USB and
most motherboards come with
FireWire as well, but it seems no
two motherboards offer the same
port arrangement. My motherboard supports eight USB ports and
two FireWire ports, for example,
but if you look on the back of the
Chapter 7: Understanding Motherboards
• Figure 7.18
Schematic of a modern chipset (courtesy of VIA Technologies)
179
180
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
Northbridge
82955X MCH
82P965
GMCH
82910G
GMCH
nForce41
nForce 570
SLI1
Chipset
Intel 975X
Express
Intel P965
Express
Intel 910GL
Express
NVIDIA
nForce4
NVIDIA
nForce 570
SLI Intel
VT8251
VT8237A
K8T900
PT890
VIA K8 Series
VIA P4 Series
Pentium 4,
Celeron
Opteron, Athlon
64, Athlon FX,
Sempron
Athlon 64,
Athlon 64 FX,
Athlon 64 X2
Intel LGA775:
Core 2 Extreme,
Core 2 Duo,
Pentium D,
Pentium 4,
Celeron D
Athlon 64,
Athlon 64 FX,
Sempron
Pentium 4 with
HT, Celeron D
All LGA775
LGA775 Core 2
Extreme, Core 2
Duo, Pentium 4,
Pentium 4 with
HT, Pentium
Extreme Edition,
Pentium D
CPU
400, 533,
800, 1066
n/a2
n/a2
533, 800,
1066
n/a2
533
533, 800,
1066
1066
800
FSB (MHz)
SDRAM with
ECC, DDR,
DDR2 up to
4 GB
n/a2
n/a2
Dual-channel
DDR2
n/a2
DDR up to
2 GB
Dual-channel
DDR2 up to
8 GB
Dual-channel
DDR2 up to
8 GB
RAM
No
No
SLI
Yes
No
No
No
No
No
No
AGP
SLI
SLI
Yes
Yes
only
1×
Yes
SLI
PCIe
2×/4×
SATA
1.5 Mbps
4× PATA
133 MBps
4× SATA
3 Gbps
4× PATA
133 MBps
6× SATA
3 Gbps
2× PATA
4× SATA
3 Gbps
4× PATA
4× SATA
1.5 Gbps
4× SATA
1.5 Gbps
6× SATA
3 Gbps
4× SATA
3 Gbps
HDD
8× USB
2.0
8× USB
2.0
10×
USB
2.0
8× USB
2.0
10×
USB
2.0
8× USB
2.0
10×
USB
2.0
8× USB
2.0
USB
No
No
No
No
No
No
No
No
FireWire
1. NVIDIA does not make a Northbridge/Southbridge distinction with the nForce chipset.
2. Because the Athlon 64 varieties and the Sempron CPUs have the memory controller built into the CPU, the frontside bus and memory clock speeds depend on the motherboard
speed rather than the chipset. The speed between the CPU and the chipset runs up to 1066 MHz, hyperthreaded. The amount of RAM supported likewise depends on the CPU
rather than the chipset.
n/a1
nForce 590
SLI1
NVIDIA nForce
590 SLI AMD
n/a1
n/a1
ICH6 or
ICH6R
P965 ICH8
82801GB ICH,
82801GR ICH,
or
82801GDH
ICH
Southbridge
Chipset Comparison Chart
Table 7.1
motherboard, you’ll only see four USB ports and one FireWire port. So,
where are the other ports? Well, this motherboard has special connectors for the other four USB and one FireWire port, and the motherboard
comes with the dongles you need to connect them (Figure 7.19). These
dongles typically use an extra slot on the back of the case.
These dongle connectors are standardized, so many cases have
built-in front USB/FireWire ports that have dongles attached. This is
very handy for USB or FireWire devices you might want to plug and
unplug frequently, such as a thumb drive or digital camera. You can
also buy add-on front USB and FireWire devices that go into a 3.5-inch
drive bay, like a floppy drive (Figure 7.20).
• Figure 7.19
USB/FireWire dongle
Sound
Quite a few motherboards come with onboard sound chips.
These sound chips are usually pretty low quality compared
to even a lower-end sound card, but onboard sound is cheap
and doesn’t take up a slot. These connectors are identical to
the ones used on sound cards.
RAID
RAID stands for redundant array of independent devices and is • Figure 7.20 Front USB and FireWire drive bay device
very common on motherboards. There are many types of
RAID, but the RAID on motherboards usually only supports mirroring (the process of using two drives to hold the
same data, which is good for safety because if one drive dies, the other still
has all the data) or striping (making two drives act as one drive by spreading
data across them, which is good for speed). RAID is a very cool but complex
topic that’s discussed in detail in my other book, Mike Meyers’ CompTIA A+
Guide: PC Technician (Exams 220-602, 220-603, & 220-604).
AMR/CNR
The U.S. Federal Communications Commission
(FCC) must certify any electronic device to ensure
that it does not transmit unwanted electronic
signals. This process is a bit expensive, so in the
very late 1990s Intel came up with a special slot
called the
audio modem riser (AMR) . See
Figure 7.21. An AMR slot was designed to take
specialized AMR devices (modems, sound cards,
and network cards). An AMR device would get one
FCC certification and then be used on as many
motherboards as the manufacturer wanted
without going through the FCC certification
process again. AMR was quickly replaced with the
more advanced communications and networking
riser (CNR) . Many motherboard manufacturers
used these slots in the early 2000s, but they’ve lost
popularity because most motherboard makers
simply use onboard networking and sound.
Chapter 7: Understanding Motherboards
• Figure 7.21
AMR slot
181
Chapter 7 Review
■ Chapter Summary
After reading this chapter and completing the
exercises, you should understand the following about
motherboards.
and picoBTX are designed to replace ATX,
microATX, and FlexATX respectively.
■
Several PC manufacturers make proprietary
motherboards, meaning they do not adhere to a
standard form factor like ATX or BTX. Servicing a
system like this can be frustrating, as parts may be
difficult to find and are often available only from
authorized dealers.
■
Motherboards come with differing features or
components such as USB/FireWire ports, audio,
video, RAID, or AMR or CNR slots for modems
and network cards. Sometimes a motherboard will
support several USB/FireWire ports, but will not
have rear ports for all of them. In this case, the
motherboard likely has connections for the
additional ports to be used in conjunction with a
dongle to create front-mounted ports.
■
Popular motherboard manufacturers include Abit,
Asus, Biostar, DFI, Gigabyte, Intel, MSI, and Shuttle.
How Motherboards Work
■
■
Every piece of hardware connects either directly or
indirectly to the motherboard. Wires called traces
make up the different buses on the system,
enabling hardware to communicate. Motherboards
are several layers thick with traces running across
each layer, creating a veritable highway of wires.
Motherboards are defined by their form factor,
chipset, and components. The form factor defines
the physical size and airflow; the chipset defines
what type of CPU, what type and how much RAM,
and what components a motherboard will support.
Types of Motherboards
■
The Advanced Technology (AT) form factor,
though now obsolete, was the predominant form
factor for motherboards through the mid-1990s. Its
identifying features included a large keyboard
plug and a split power socket called P8/P9.
■
LPX and NLX were slimline form factors, meaning
they were ideal for low-profile cases. They offered
a central riser slot to accept a special riser card into
which expansion cards fit horizontally.
■
The Advanced Technology Extended (ATX) form
factor replaced the AT as the form factor of choice
by the late 1990s. It offered several improvements
over the AT, including repositioning the power
supply for better airflow, easier access to CPU and
RAM slots, and better performance by moving
RAM closer to the Northbridge and CPU. The
microATX (μATX) and FlexATX are subtypes of
the ATX and are considerably smaller than the
ATX.
■
182
The Balanced Technology eXtended (BTX) form
factor is newer than ATX and was designed to
improve cooling. BTX cases take cool air in from
the front and blow warm air out the back. As BTX
motherboards place the CPU towards the front of
the case, the CPU receives additional cooling from
the improved airflow. Standard BTX, microBTX,
Chipset Varieties
■
Every motherboard has a chipset that determines
the type of CPU the motherboard supports, the
type and capacity of RAM, and what devices the
motherboard supports without an expansion card.
Most modern chipsets are composed of two
primary chips—the Northbridge and the
Southbridge. As the Northbridge works with the
CPU and RAM, it gets very hot, and therefore
needs its own heat sink and fan. The Southbridge
usually does not require any extra cooling and is
thus exposed, making it a great place to find the
stamp of the chipset manufacturer.
■
As almost no modern chipset supports old
technologies like floppy disk drives, infrared
connections, and parallel ports, motherboards
contain a third chip called the Super I/O chip to
support these technologies. The Super I/O chip is
not part of the chipset.
■
The system ROM chip provides basic support for
the chipset, but to benefit from all the features of a
chipset, you need to install the operating system–
specific driver for the chipset once you’ve installed
the operating system.
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
■
Chipset manufacturers for AMD-based motherboards
tend to use the terms Northbridge and Southbridge,
whereas Intel-based boards tend to use different
terminology. You might see the Northbridge
referred to as the Memory Controller Hub (MCH)
and the Southbridge referred to as the I/O Controller
Hub (ICH).
■
Popular chipset manufacturers today include Intel,
AMD, NVIDIA, and VIA.
■ Key Terms
AT (170)
ATX (173)
audio modem riser (AMR) (181)
Balanced Technology eXtended
(BTX) (175)
chipset (169)
communications and networking
riser (CNR) (181)
FlexATX (174)
form factor (169)
I/O Controller Hub (ICH) (178)
LPX (171)
Memory Controller Hub
(MCH) (178)
microATX ( ATX) (174)
microBTX (175)
motherboard (168)
NLX (171)
NVIDIA Corporation (178)
P8/P9 (170)
picoBTX (175)
riser card (171)
slimline (171)
Super I/O chip (177)
thermal unit (175)
traces (168)
VIA Technologies (178)
■ Key Term Quiz
Use the Key Terms list to complete the sentences that
follow. Not all terms will be used.
1. The ____________ defines the type of processor
and RAM required for the motherboard and
determines to a degree the built-in devices
supported by a motherboard, including the
expansion slots.
5. The ____________ determines the physical size of
the motherboard as well as the general location
of components and ports.
6. The smallest ATX motherboard form factor is the
____________.
7. The smallest BTX motherboard form factor is the
____________.
2. The AT type of motherboard had a unique, split
power socket called ____________.
8. The fan of the BTX ____________ blows the hot
CPU air directly out the back of the case.
3. The ____________ form factor replaced the LPX
slimline form factor.
9. Small wires on the motherboard, called
_______________, make up the different buses on
a system.
4. Everything in the ____________ form factor is
designed to improve cooling.
10. Older technologies, such as the floppy drive and
parallel ports, are now handled by the
_______________.
■ Multiple-Choice Quiz
1. Which of the following are part of the ATX form
factor? (Select two.)
2. Which of the following form factors dominates
the PC market?
A. FlexATX
A. AT
B. macroATX
B. ATX
C. microATX
C. BTX
D. picoATX
D. NLX
Chapter 7: Understanding Motherboards
183
3. The nonprofit where Sid works received a
half-dozen new motherboards as a donation.
When he went to install one into a case, however,
it didn’t fit. The ports and expansion slots seemed
to be switched. What’s most likely the issue?
A. Sid’s trying to install a proprietary
motherboard into an ATX case.
B. Sid’s trying to install an LPX motherboard
into an ATX case.
C. Sid’s trying to install a microATX
motherboard into an ATX case.
D. Sid’s trying to install a microBTX
motherboard into an ATX case.
4. Troubleshooting a system, Sarah finds that
everything works except the floppy drive and
parallel port. Even using a known good floppy
drive and cable, and a working parallel Zip
drive, she can’t get either device to function.
What is most likely at fault?
A. Floppy/parallel bridge
B. Northbridge
C. Southbridge
D. Super I/O
5. On Intel-based motherboards, which chip
enables the CPU to interact with RAM?
A. Memorybridge
7. Which of the following chips enables an Athlon
64 to use dual-channel DDR RAM?
A. ATI 200 Express
B. NVIDIA nForce 570 SLI Intel
C. NVIDIA nForce 590 SLI AMD
D. None of the above
8. Steve has been tasked to upgrade ten systems at
his office. The systems currently have microATX
motherboards with 512 MB of DDR RAM and
Athlon XP CPUs.
Primary objective: Upgrade ten systems.
Optional objectives: Use the current cases and
use the current RAM.
Proposed solution: Purchase ten microATX
motherboards with NVIDIA nForce 570 SLI Intel
chipsets and ten Pentium D CPUs.
The proposed solution:
A. Accomplishes only the primary objective.
B. Accomplishes the primary objective and one
of the optional objectives.
C. Accomplishes the primary objective and both
of the optional objectives.
D. Accomplishes neither the primary nor the
optional objectives.
9. Which of the following companies make
chipsets?
B. Northbridge
A. AMI
C. Southbridge
B. Gigabyte
D. Super I/O
C. MSI
6. Brian bought a new motherboard that advertised
support for eight USB ports. When he pulled the
motherboard out of the box, however, he found
that it only had four USB ports. What’s likely the
issue here?
A. The extra four USB ports will connect to the
front of the case or via a dongle to an
expansion slot.
B. The extra four USB ports require an add-on
expansion card.
D. VIA
10. How are expansion cards installed on LPX and
NLX motherboards?
A. Via the onboard ISA and PCI slots
B. Via a riser card
C. Via MCA and XT slots
D. Expansion cards cannot be installed in LPX
and NLX motherboards.
C. The FireWire port will have a splitter that
makes it four USB ports.
D. The motherboard chipset might support eight
USB ports, but the manufacturer only
included four ports.
184
Mike Meyers’ CompTIA A+ Guide: Essentials (Exam 220-601)
■ Essay Quiz
1. This chapter talks about motherboards made
in layers that contain the wires or traces. If
necessary, find an Internet site that talks about
the motherboard manufacturing process. Why
do you think motherboards are made in layers?
What advantages do the layers provide?
2. Some people believe that selecting a motherboard
based on the motherboard chipset is an even
more important decision than basing the decision
on the kind of processor. Do you agree or disagree
and why?
Lab Projects
• Lab Project 7.1
Examine all the ports and connectors on the back of
your computer. With the computer turned off, you
may disconnect the cables from the ports. (If
necessary, document where and how the cables are
connected so you can replace them correctly.)
Determine the kinds of ports that are built in and
those that are provided by expansion cards. From
this information alone, ascertain whether your
motherboard is an AT or an ATX form factor. Draw
a diagram of the back of your system and label every
port and all connectors. State if their sources are
from the motherboard or from an expansion card.
Lastly, state the form factor of the motherboard.
• Lab Project 7.2
One of the most important skills that a PC technician
can possess is the ability to read and interpret
documentation. No single piece of documentation is
as important as the motherboard book. Let’s see how
well you can understand this documentation.
Consult your motherboard book or use one that your
instructor provides. (If you do not have the
motherboard book, try to download it from the
manufacturer’s Web site.) Then write a paragraph
about your motherboard that includes answers to
the following questions:
■
What make and model is the motherboard?
■
What chipset does it use?
■
What kinds of RAM slots does it contain?
■
What kinds of expansion slots does your
motherboard have and how many of each
kind does it have?
Chapter 7: Understanding Motherboards
■
What kinds of onboard ports does it have?
■
What kinds of CPUs does it support and what
kind of processor slot does it have?
■
Does your motherboard use jumpers or dip
switches for configuration? If so, what do the
jumpers or dip switches control?
■
The motherboard book probably contains an
illustration of the way that the motherboard
components are laid out. By examining this
illustration, determine what form factor your
motherboard uses.
■
Does your motherboard have any unusual or
proprietary features?
185