Transcript Motherboardx

Motherboard
Introduction
• the large circuit board inside your computer's
case.
• Sometimes called the system board, the logic
board, the baseboard or the planar board.
• Everything connected to the computer system,
plugs either directly or indirectly into the
motherboard
• Some therefore think of it as the central
nervous system of the computer
What do we mean?
• The Central Processing Unit (CPU) sits on the motherboard
• The motherboard also contains the Basic Input/ Output
System (BIOS) chip and the CMOS Setup information.
• It has expansion slots for installing different adapter cards e.g.
video card, sound card, Network Interface Card (NIC) and
modem.
• This circuit board provides a connector for the keyboard as
well as housing the keyboard controller chip.
• It has the system's Random Access Memory (RAM) slots,
provides the system's chipset, controllers and the bus system
Types of Motherboards
• Non-integrated motherboard
• Integrated/embedded motherboard
Non- Integrated Motherboards
• Non-Integrated Motherboards have
assemblies installed as expansion boards.
• The assemblies mentioned above include the
I/O Port connectors (serial and parallel ports),
hard drive connectors or paddle boards,
floppy controllers and connectors, joystick
connections...
• Most of the older motherboards were NonIntegrated.
Advantages of Non- Integrated
Motherboards
• Mainly lies in cost.. i.e.
• The individual motherboard is relatively cheap to
produce.
• should something go wrong with the individual
assemblies, such as a bent or broken pin in a
connector, or a defective controller chip, one
could repair the problem by replacing the
individual expansion card at a relatively cheaper
cost than to replace the whole board
Disadvantage of Non-Integrated
Motherboards
• Main disadvantage with this board is that it
takes up one or more of the motherboard's
expansion slots and reduces the amount of
free space inside your computer's case, which
would also limit expansion
• As well, because of the cost of manufacturing,
testing and installing the expansion boards
individually, there's an added cost to the
overall computer system.
Integrated Motherboards
• Some of the later 486 system boards began to
integrate some of these assemblies right onto the
circuit board i.e. they are installed or built right
onto the board
• The serial and parallel ports, the IDE and floppy
drive, and joystick all connect directly to the
motherboard.
• Other technologies integrated included video,
sound, networking and modems right onto the
system board.
Advantage of Integrated
Motherboards
• Cost and affordability is a concern for any manufacturer.
Make your product more affordable, and more people will
buy it, creating a larger market and increased sales. This is
actually the whole idea behind the integrated motherboards
• Reduction in cost - there's less material involved, less
installation, and testing can all be done at the same time
• Better compatibility - the more things that are done by a
single chip or group of chips from one manufacturer, the
simpler the design is.
• Less chance of a problem - integrated assemblies are
generally quite stable and even though problems occur, they
tend to be rare.
• Integration also frees up some space inside the case and
allows for better accessibility and airflow
Downside of Integrated Motherboards
• What happens if one of the embedded technologies
gives out or there is a controller failure or broken pin?
The solution would be to either repair it, which is quite
expensive or to replace the motherboard.
• Some manufacturer have provision to upgrade or bypass
a particular feature by installing an adapter card and
disabling the embedded device. There are, however,
problems with this:
• An ordinary user might have difficulties with disabling
the current assembly. Some are disabled as soon as you
install another device (such as a video card in an AGP
slot). Others have to be disabled through software setup
programs, or in your system's CMOS setup, or by setting
jumpers on the motherboard itself
Downside of Integrated Motherboards
ctd.
• Is it possible to upgrade to the device? Is there a list of the
compatible devices? A lot of embedded system boards can
be fussy about the model and manufacturer of the device
you're using to replace an embedded feature.
• Is there room for the upgrade? Eg. embedded video
technology has 4 megabytes of video RAM, upgradeable to,
say 12MB. What this generally means is that there is 4MB
of Video RAM, which is faster than regular system RAM and
when upgraded to 12 MB, it will use 8MB of the system's
RAM
• Newer video technology now uses regular system RAM
instead of faster VRAM, and the 64 MB computer now has
only 56 MB of memory, because 8MB has been allocated to
video
Motherboard Components
Here, we identify the various components found on the motherboard plus a brief description of each.
Motherboards vary, one may find more or fewer chips or devices on your board, depending on its age
and level of integration. However, these are the most common items found on a typical modern
motherboard.
• Printed Circuit Board
• Processor Sockets or Slots
• Memory Sockets
• Cache Sockets
• I/O Bus Slots
• Power Connector(s)
• Voltage Regulators
• Capacitors
• Keyboard and Mouse Connectors
• Keyboard Controller
• Real-Time Clock and CMOS Memory Chip
• Super I/O Controller
• BIOS Chips
• Battery
• Jumpers
• Ports and Headers
• Pin Connectors
• System Chipsets and Controllers
Printed Circuit Board
• The motherboards is essentially a multiple layer
printed circuit boards, also called PCBs. The physical
board we see is actually a sandwich of several thinner
layers, each containing some of the circuitry required
to connect the various components on the board
• At one time this was expensive, difficult-tomanufacture technology, but time and automation has
reduced this complexity to the point where the board
itself is a minor component of overall cost.
• It is important to note that thin boards are subject to
damage from flexing when inserting peripherals
• Rule of thumb: the thicker the board, the better.
Processor Sockets
• The motherboard has one or more sockets or slots to hold the processor(s).
• Single-processor motherboards are common, but dual processor and quad
processor boards can be found. (Quad boards often use special, proprietary
designs employing riser cards.)
• The type of socket or slot used dictates the type of processor (and in some
cases the speed) that can be used by the motherboard.
• Most modern motherboards that have a socket use the ZIF (zero insertion
force) style socket, which allows the processor to be inserted or removed
from the motherboard by using a lever that tightens or loosens the
processor's pins in the socket. This is a vast improvement over the older
style sockets, which required you to exert considerable force on the surface
of a delicate (and expensive) processor, just to get it into the motherboard
Memory Sockets
• Most motherboards have between 2 and 8
sockets for memory. These are either SIMMs
(single inline memory modules) or DIMMs (dual
inline memory modules)
• These sockets are labelled "SIMM0" through
"SIMM7" or "DIMM1" through "DIMM3", etc. The
sockets are almost always filled starting with the
lowest numbered socket first.
• Most Pentium class or higher motherboards
require SIMMs to be inserted in pairs, but DIMMs
may be inserted individually
Cache Sockets
• Virtually all newer 486 or Pentium class motherboards come with
either integrated secondary cache or sockets for secondary cache to
be inserted.
• Also called "Level 2" or "L2" cache, secondary cache is high-speed
memory that is used to buffer processor requests to the regular
system memory. Either 256 KB or 512 KB of cache is most common,
with larger sizes such as 1 MB and higher now coming onto the
market. Motherboards for Pentium Pro and Pentium II PCs don't
have level 2 cache on them; it is already integrated into the
processor itself for the Pentium Pro
• Motherboards typically have either cache chips soldered directly
into the board, sockets for cache chips, or a socket for COASt, or
"cache on a stick". This socket is sometimes called a CELP ("card
edge low profile").
I/O Bus Slots
• All motherboards have one or more system I/O buses, which are
used to expand the computer's capabilities. The slots in the back of
the machine are where expansion cards are placed (like your video
card, sound card, network card, etc.)
• 3 types of slots: ISA (Industry Standard Architecture) bus slot, PCI
(Peripheral Component Interconnect) bus slot and an AGP
(Accelerated Graphics Port) slot.
• The first bus slot, ISA; most PCs have 3 or 4 of these. These slots
have two connected sections and start about a half-inch from the
back of the motherboard, extending to around its middle. This is
the oldest (and slowest) bus type and is used for cards that don't
require a lot of speed: for example, sound cards and modems.
• Older systems (generally made well before 1990) may have ISA slots
with only a single connector piece on each; these are 8-bit ISA slots
and will (of course) only support 8-bit ISA cards.
I/O Bus Slots ctd
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•
•
Pentium systems and newer 486-class motherboards also have PCI bus slots, again,
usually 3 or 4. They are distinguished from ISA slots in two ways. First, they are
shorter, and second, they are offset from the back edge of the motherboard by
about an inch. PCI is a high-speed bus used for devices like video cards, hard disk
controllers, and high-speed network cards.
Newer PCs add another, new connector to the motherboard: AGP slot. This is not
really a bus, but is a single-device port used for high-performance graphics. The
AGP slot looks similar to a PCI slot, except that it is offset further from the back
edge of the motherboard.
Some motherboards incorporate a so-called "shared" ISA and PCI slot. This is a
single slot that can take either type of card, but that isn't possible because the two
slot types are physically incompatible. In order to save space while maximizing the
number of expansion slots, some designers put an ISA slot on the board right next
to a PCI slot; you then have the choice to use either the ISA or the PCI slot, but not
both. This design is possible because ISA cards mount on the left-hand side of a
slot position, while PCI slots mount on the right-hand side.
Power Connector(s)
• The motherboard has a socket to attach the
power cables coming from the power supply. As
discussed in the power supply chapter ATX forms
factor motherboards and power supplies use a
single, keyed 20-wire motherboard power cable.
All others use a pair of 6-wire cables. The cables
are connected to the motherboard so that the
black wires (grounds) are together in the middle.
• This connector is usually found near the back
right-hand side of the motherboard, near the
power supply.
Voltage Regulators
• The advent of processors and other devices running at different
voltages--in the "old days" they all used to run at the 5V provided
by a standard power supply--has led to the necessity of one or
more voltage regulators on most modern motherboards. These
regulators reduce the 5V signal to those voltages typically needed
by processors: 3.3V or lower.
• The voltage regulator can normally be identified by the large
heatsinks that are placed on it; voltage conversion generates a great
deal of heat. The regulator is controlled via processor voltage
jumpers, which are set to the appropriate voltage for the processor
being used. On many motherboards the cooling level of the entire
system case is important to ensuring that the voltage regulators are
cooled satisfactorily. Overheating regulators can cause lockups and
other problems.
Capacitors
• Capacitors are electrical components that are used to filter and
smooth signals on the motherboard. For the most part, they receive
relatively little attention since they are passive and not very
exciting. However, recently many motherboard manufacturers have
been skimping on capacitors by either reducing the number on the
board, or using smaller or cheaper ones. Over time, cheaper
capacitors tend to dry out and lose their effectiveness. The result of
this corner-cutting is possibly spurious signals on the board (causing
problems that are virtually impossible to troubleshoot) and reduced
motherboard life.
• The only real way to protect against this sort of cheap construction
is to avoid buying motherboards only on the basis of price. Look for
name brands on the capacitors, and to make sure that they are a
good size.
• Capacitors of the type used on motherboards generally come in
two flavors: tantalum or electrolytic.
Keyboard and Mouse Connectors
• The types of keyboard and mouse connectors your PC will have
depend on the style and form factor of your motherboard. There
are generally two arrangements.
• Newer PCs, PCs using the ATX, LPX or NLX form factors, and many
proprietary (brand name) machines, use a pair of small 6-pin
connectors for the keyboard and dedicated (PS/2) mouse.
• Older PCs using the AT form factor use the older, large, 5-pin
keyboard connector, and do not have a dedicated mouse port
connector. These PCs use a serial port for the mouse.
• Some motherboards don't come with a built-in PS/2 mouse port,
but include a header for a PS/2 mouse port, which you can use to
add a PS/2 mouse port yourself.
• These connectors are located at the back of the motherboard.
Keyboard Controller
• The keyboard controller does what the name
implies. It also controls the built-in PS/2 port,
if it exists on the motherboard. On some
newer PCs, this controller is in fact further
integrated into the Super I/O controller chip,
so your motherboard may not have a separate
chip for it.
Real-Time Clock and CMOS Memory
Chip
• This chip holds the real-time clock that keeps
the date and time on your PC, as well as the
CMOS RAM that holds your PC's BIOS settings.
It is powered by the PC's built in battery,
which may in some cases be built into the
real-time clock package itself. This chip is
often marked "Dallas", after Dallas
Semiconductor, the company that makes a
large number of them.
Super I/O Controller
• The Super I/O controller chip performs many
of the standard input/output functions that
used to be done by multiple smaller chips.
National Semiconductor makes a large number
of these chips, and they can sometimes be
identified by looking for this name on the
surface of the chip.
Battery
• The PC uses a low-power battery to
maintain certain information when the
power is off; for example, your BIOS
settings, the current date and time, and
resource assignment for Plug and Play
systems.
• Some PCs use a battery soldered to the
board that looks like a small cylinder or
barrel. It is not generally detachable.
• Some PCs use a flat round watch
battery in a metal holder.
BIOS Chips
• The system BIOS is coded into read-only memory
(ROM) chips that are placed on your motherboard.
There are usually one or two BIOS chips, depending
on the board, and often labeled with the name of the
BIOS software company (usually Award or AMI)
• Some PCs don't appear to have a battery at all. In this
case, the battery may be a lithium type that is within
one of the other packages (typically the real-time
clock package). It may also be an integrated
rechargeable Nickel-Cadmium battery (sometimes
called an "accumulator") that is recharged whenever
the line power is connected to the machine. These
batteries cannot be replaced, although they are rated
for a long life (5 to 10 years).
• JP1, JP2 etc. For some functions, a group of jumpers
is used.
Jumpers
Jumpers are pins on a motherboard or other device, that are used to provide
configuration information to the hardware. A single jumper consists of a pair of
pins, with a small rectangular shunt that can be placed over both pins to short
them together. The hardware is programmed to act one way when the jumper is
shorted, and another way when it is left open. The jumpers are normally numbered
One of the newest innovations on the market is the "jumperless" motherboard,
such as the IT5H made by Abit. With these boards you make many of the hardware
settings, such as CPU type and speed, and even CPU voltage, using BIOS settings,
while some others are retained as regular jumpers (typically, CMOS clear and
cache size). This arrangement lets you change the clock speed of the CPU as easily
as you would change any other BIOS setting, and makes upgrading the processor a
snap. It also makes it easier for motherboard manufacturers to add support for
new processor types as they are put onto the market.
Many people think that "jumperless" is the new wave of motherboard design, and
certainly the ability to change more settings without opening up the box is a great
advantage. Others like the control of being able to physically set a jumper
Every motherboard differs in its jumper numbering, positioning, and most importantly, what the
settings for each jumper mean. This is why having the motherboard manual is so crucial for any
technician who is troubleshooting a PC. This procedure provides specific instructions and caveats for
configuring your motherboard.
Ports and Headers
• Ports are connectors used to connect external cables and devices to the
motherboard. In addition to the keyboard and PS/2 mouse connectors, some
types of motherboards (such as the ATX) have on the back edge of the
motherboard integrated serial and parallel ports.
• Motherboards that don't use integrated ports, use headers on the
motherboard instead. Headers are groups of pins used to connect devices or
ports to the motherboard. A cable runs from the port and is plugged into the
header on the board. The following are the headers that are commonly found
on a typical Baby AT style motherboard (though some of the functions are
provided as headers to ATX style boards as well, if an integrated port is not
provided):
• Serial Ports: As mentioned, there are usually two serial port headers. Each
has 9 or 10 pins (only the first 9 are used, however).
• Parallel Port: This header is used for the external parallel port and has 26
pins (25 are actually used).
• PS/2 Mouse Port: Some good motherboards provide a header for a PS/2
mouse port when this port is not already on the board. This lets you add a
PS/2 port yourself. The PS/2 mouse header has 5 pins.
Ports and Headers Ctd.
• USB (Universal Serial Bus): A new technology, USB is proposed to be the new
standard for connecting devices such as keyboards, mice and external modems
to the PC. Since it is not in common use yet, many motherboards provide a
header for you to run a port for it in the future if needed, instead of an actual
port (which will appear on future boards if and when USB catches on). This
header has 10 pins.
• IR (Infrared) Port: Some motherboards have a header to allow you to run a
connection for an infrared communications port, typically used for wireless
communication to printers and similar devices. Infrared ports are far more
common on laptop computers than desktop machines. These headers have 4
or 5 pins.
• Primary and Secondary IDE/ATA Hard Disk Interface: Most newer
motherboards have integrated headers for two IDE channels. Each has 40 pins.
• Floppy Disk Interface: Almost all new motherboards provide a 34-pin header
for the floppy disk cable.
• SCSI: Some motherboards have integrated SCSI ports or headers, though they
are uncommon. They are either 50 or 68 pins in size, depending on the flavor
of SCSI implemented.
Pin Connectors
• The motherboard provides several connectors that are attached to the
case LEDs, indicators, and switches. These (as usual) vary by motherboard,
but the ones described here are typical. The physical layout of these
connectors can vary a lot as well; some motherboards physically separate
these connectors on the board while others group many together into a
large "multifunction connector". Functionally there is no difference but it
is easier to make an "off by one" connection mistake on a multifunction
connector.
• These are the pin connectors you will typically find on a modern
motherboard:
• Power LED and Keylock Switch: These are two different functions, each
requiring two pins, but for historical reasons, they are often combined into
a single 5-pin connector. Older cases had the keylock and power LED wires
going to a single 5-pin plastic connector. On newer cases they are often
separated (in fact many newer cases have no keylock switch) but the 5-pin
motherboard connector remains for compatibility. Here is its usual
configuration. Note the unused pin between the two power LED pins:
Pin Connectors Ctd.
• Reset Switch: This 2-pin switch has no polarity so you can connect it
either way.
• Turbo Switch: Another relic of the past, many motherboards still
include this connector, even though it ceased having any real
meaningful purpose after the early part of the 486 generation of
motherboards. In most cases it is best just to leave it unconnected.
• Power Switch: On ATX systems there will be a connector for
attaching two leads from the case power on/off button. On ATX PCs
the power switch sends a signal to the motherboard to turn on the
PC; it doesn't attach directly to the power supply as it does on older
AT style systems.
• Turbo LED: This is the counterpart to the turbo switch of course.
Pin Connectors Ctd.
•
•
•
•
•
IDE/ATA Hard Disk Activity LED: This connector signals the LED when the
motherboard detects activity on any of the system's IDE hard disks. Some
motherboards have four pins for this connector. On many of these the four pins
represent two different pairs, both of which work: pins 1 and 2 are one pair and 3
and 4 are another, and either pair can be used. On other motherboards, only two
of the pins can be used; you need to check your motherboard manual.
Speaker: This is a 4-pin connector for the case speaker, but only the two outer
wires are used. There is no polarity here either, you can connect the speaker either
way.
CPU Fan: Some motherboards have a 2-pin connector for powering the processor's
fan, if the fan has the right type of power connector. Many fans just connect to the
regular power connectors from the power supply.
Suspend Mode Switch: Some systems have a two-pin connector for a toggle switch
to put the system into suspend mode. The turbo switch button on the case can be
used for this function on newer systems.
Suspend Mode LED: Some systems have a connection for an LED that is lit when
the system enters suspend mode, either by using the suspend mode switch or
through automatic power management.
System Chipset and Controllers
• The system chipset and controllers are the logic
circuits that are the intelligence of the
motherboard. They are the "traffic cops" of the
computer, controlling data transfers between the
processor, cache, system buses, and peripherals-basically everything inside the computer. Since
data flow is such a critical issue in the operation
and performance of so many parts of the
computer, the chipset is one of the few
components that have a truly major impact on
your PC's quality, feature set, and speed.
System Chipset and Controllers Ctd.
• What exactly is a "chipset"? A chipset is just a set of
chips. At one time, most of the functions of the chipset
were performed by multiple, smaller controller chips.
There was a separate chip (often more than one) for
each function: controlling the cache, performing direct
memory access (DMA), handling interrupts,
transferring data over the I/O bus, etc. Over time these
chips were integrated to form a single set of chips, or
chipset, that implements the various control features
on the motherboard. This mirrors the evolution of the
microprocessor itself: at one time many of the features
on a Pentium for example were on separate chips.
System Chipset and Controllers Ctd.
• The system chipset in most cases does not integrate all
of the circuitry needed by the motherboard. Most
motherboards have the following controllers on them:
• The system chipset itself.
• The keyboard controller, which manages not only the
keyboard but also the integrated PS/2 mouse
• The "Super I/O" chip, which handles input and output
from the serial ports, parallel port, floppy disks, and in
some cases, the IDE hard disks as well
• Additional built-in controllers that are normally found
in expansion cards: video, sound, network and SCSI
controllers being the most common.
Additional Integrated Motherboard
Functions
• On some motherboards, circuitry is included to
perform some of the common functions normally
found on expansion cards. This definitely has its pros
and cons, depending on what is included, how they do
it, and what your needs are. In general, incorporating
built-in circuitry has the advantage of lower cost, and
the disadvantage of lower choice and upgradability.
• Integrated Motherboard Video
• Integrated Sound "Card"
• Integrated Network Interface
• Integrated SCSI Controller
Integrated Motherboard Video
• The video card is one of the more important performancerelated features on a PC; having it included on the
motherboard eliminates the possibility of choosing a card
to meet your particular needs.
• In addition, motherboards with integrated video are
notoriously difficult to upgrade. Many that have an option
(via jumper or BIOS setting) to disable the on-board video
actually still have problems with an add-in upgrade video
card, and many come with no ability to disable the built-in
video at all! On a lower-end machine however, integrated
video can save some cost over buying a separate video
card, as well as an expansion slot. These motherboards are
often found in the LPX form factor, where saving space and
cost is normally a priority.
Integrated Sound Card
• Integrated sound support is fairly common,
particularly on retail brand-name machines. Even
the lesser clones have figured out by now how to
do basic SoundBlaster emulation. However, bear
in mind that sound cards use many system
resources and can cause many hard-to-diagnose
problems when they are of low quality. Most of
the integrated devices provide rather basic
functionality not approaching the high-end
capabilities of the real add-in cards.
Integrated Network Interface
• Integrated network adapters are relatively
rare on motherboards though all branded
workstations nowadays come with inbuilt
10/100Mbps card. In some ways, this is one of
the least offensive of the integrated
controllers discussed in this section, provided
it emulates a common standard (such as
NE2000-compatible 10 /100Mb/second
Ethernet), and it comes with good drivers.
Integrated SCSI Controller
• Some motherboards come with built-in
motherboard SCSI support.
• One of the problems with SCSI is the large
number of constantly changing standards and
protocols.
Extras for the motherboard
In addition to the motherboard itself, a good quality
motherboard should come with the items described
in this section::
•
•
•
•
Motherboard Manual
I/O Connectors
Floppy Cable
IDE/ATA Interface Cable
Motherboard Manual
• General Information: The model number of the board,
the name of the manufacturer, and contact information.
You need this to get help, BIOS upgrades or information
on your board.
• Assembly Instructions: Instructions on how to install,
jumper, and configure the board. Some motherboards
put this on a single page; others include a 50-page-plus
manual. This should include a diagram of the board
showing where all the components are. If this diagram
doesn't look like the actual board (it happens!) you
could have trouble, but not always. It is also fairly
common for there to be slight differences between what
is actually on the board and what the manual says. Be
very careful to watch for these.
Motherboard Manual ctd.
• Configuration Information: Information on acceptable
processor and memory configurations for the board. You
need this information to determine what processor and
system memory to buy.
• BIOS Manual: An explanation of the board's BIOS settings,
what they mean, and how you should set up the machine.
These manuals (which are sometimes separate from the
motherboard manual and sometimes just a second section
in a single manual) range in size and quality much like the
assembly instructions. However, there are many Internet
resources to help with BIOS settings. Motherboard
assembly instructions are much more board-specific and so
are harder to find outside the manual itself.
I/O Cables or Connectors
• If your motherboard uses the ATX, LPX or NLX form
factors, it has integrated serial and parallel port
connectors.
• If it is AT or Baby AT style, then you normally should get
three ribbon cables with the motherboard to connect
the serial and parallel connectors to the motherboard.
• The serial cables normally have 9 wires each (even if
they go to 25-pin connectors) and the parallel cable has
25. These connectors normally come pre-mounted into
metal inserts intended to be installed into the case
where expansion cards go.
Floppy Cable
• The motherboard should come with one
"standard" 34-pin floppy disk cables. This is
the unusual-looking cable with 5 connectors
on it (one plus two pairs), with a half-twist in 7
of the wires in the middle of the cable.
IDE/ATA Interface Cable
• A motherboard normally comes with one standard 40pin IDE (ATA) hard disk / CD-ROM cable. It should have
3 connectors on it, but sometimes will only have 2. If
you want to use two IDE channels (which is preferred in
most cases for performance reasons), you will usually
have to use an additional interface cable.
• A standard, 40-wire IDE/ATA cable. Note the presence
of three black
connectors, and the 40 individual wires in the ribbon
cable. Also note the red
wire that marks wire #1 and hence pin #1 on each
connector.
In conclusion…
• A good motherboard should be solid and well
designed
• Such boards reduce interference problems
because of their design, and reduce the chances
of problems in assembling the PC.
• Cheaper flimsy boards increase chances of a
(virtually impossible to diagnose) electrical
problem on the board
• The motherboard also defines the computer
type, upgradeability and expansion capability