Motherboards
Jamie Tees
The motherboard is the essential main hardware in every computer system. Every piece of hardware
plugs directly into this board.
Form Factors
AT
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Invented by IBM in the early 1980’s
Now obsolete
Few variations of size from big to very big
Original AT Board was 12” by 12”
Only port was for a keyboard
LPX
 First slimline form factor
 Stands for low profile extended
^ This is slightly controversial
NLX
 Replaced the LPX form factor
 Doesn’t stand for anything just a real cool name.
Note: Both the LPX and the NLX provided a central riser slot for a riser card. This was called a
Daughterboard. This allowed expansion cards to fit into the Daughterboard horizontally.
N.B: An apple a day keeps the doctor away.
ATX
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Invented in 1995
No AT keyboard port, it was replaced with a mini-DIN (PS/2) port.
Position of the PSU was at a better angle.
CPU + RAM positioned for easier access
RAM closer to the CPU + Northbridge
Average size was 12” x 9.6”
Micro ATX (µATX)
 30% smaller than ATX
 Uses the same connections
 Average size was 9.6” x 9.6”
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Motherboards
Jamie Tees
Flex ATX
 Smallest ATX variant
 Average size is 9” x 7.5”
 Also used the same connections
ITX
 Available in 2001
 Is a SFF board (Small form factor)
 6.7” x 6.7”
Nano and Pico – ITX
 Nano (4.7” x 4.7”)
 Pico (3.8” x 2.8”)
 Used for special routers / embedded devices
Proprietary Form Factors
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Main culprits (Dell / Sony)
Boards are meant for certain cases only
Laptops have no form factor they are all proprietary
Drives us techie’s nuts when we need replacements.
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Motherboards
Jamie Tees
Expansion Slots and the Expansion Bus
Expansion Bus
 Expansion slots are connected to either the North or South Bridge.
 Sometimes some slots are connected to the North Bridge and others to the South Bridge
 Plug in a HDD controller card and you will be able to use it as normal, only difference may be
speed of use, E.G maybe slower using an expansion slot than using on board controllers.
 Expansion slots use a different crystal for the speed of the bus.
Types of Expansion Slots
PCI
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Peripheral Component Interconnect (Intel)
Introduced in the early 1990’s
Lack of price tag made manufacture’s quickly adopt this slot
Originally ran at 33 MHz and was 32 bit
Can co-exsist with other expansion buses
Self configuring and featured PnP
There was a 64 bit version of PCI but it is very rare
AGP
 Accelerated Graphics Port
 Guess what it’s used for ;)
PCI-X
 PCI Extended is a 64 bit wide bus
 Will accept regular PCI cards
 More enhanced speeds (PCI-X 66, PCI-x 133, PCI-X 266 + PCI-x 533)
Mini-PCI
 Version of PCI for laptops
 Mainly used for Wi-Fi and Bluetooth internal cards
PCIe (PCI Express)
 Fastest version of PCI
 Uses new method (Point to Point) Serial communication PCI uses share parrell
communication
 Has multiple speeds and revisions
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Motherboards
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Expansion Buses Comparison
Bus
Bus Type
Address Lines
Local
Data Path
(Bits)
64
PCIe V2
Local Video
and Local I/O
Serial with up
to 32 lanes
Up to 32 lanes
Bus
Frequency
Up to 1600
Mhz
2.5 GHz
System bus
PCIe V1.1
Local Video
and Local I/O
Serial with up
to 16 lanes
Up to 16 lanes
1.25 GHz
PCIe V1
Local Video
and Local I/O
Serial with up
to 16 lanes
Up to 16 lanes
1.25 GHz
PCI-X
Local I/O
64
32
PCI
Local I/O
32 or 64
32 or 64
66, 133, 266
or 533MHz
33, 66 MHz
AGP 1x, 2x,
3x, 4x, 8x
FireWire 400
and 800
USB 1.1, 2.0
and 3.0
Local Video
32
NA
Local I/O or
Expansion
Expansion
1
Serial
66, 75, 100
MHz
NA
1
Serial
3 MHz
Motherboard Chips
the External Databus
(Chips, hmmm I’m hungry)
32 or 64
Throughput
Up to 3.2
GB/sec
Up to 500
MB/sec per
lane in each
direction
Up to 250
MB/sec per
lane in each
direction
Up to 250
MB/sec per
lane in each
direction
Up to 8.5
GB/sec
133, 266 or
532 MB/sec
266 MB/sec to
2.1 GB/sec
Up to 800
MB/sec
12 or 480 Mbs
or 5.0 Gbps
et, The Address Bus and
North Bridge
 Deals with high speed interfaces such as RAM / Graphics Card
South Bridge
 Controls lower speed hardware such as USB ports and peripheral ports.
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Motherboards
Jamie Tees
Modern CPU’s now contain the North Bridge instead of it on being on the motherboard nowadays
the motherboard is refered to differently also:
 Intel (ICH) Input/Output Controller Hub
 AMD (FCH) Fusion Controller Hub
 The chipset extends the data bus to every device on the PC and the cpu uses the data bus to
move data to and from all the devices on the CPU.
 Data constantly flows on the external databus between / among the CPU, Chipset, RAM and
other devices.
Address Bus
 For the CPU to tell the chipset to send / store data in the memory and it also tells the chipset
which section of memory to access and use.
External Databus
 The chipset extends the address bus to all of the devices this way the cpu can use the
address bus to send commands to devices just as it communicates with the chipset.
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