AT
& Baby
AT -
Prior to 1997, IBM computers
used large motherboards.
After that, however, the size of the motherboard
was reduced and boards
using the AT
(Advanced Technology) form
factor was released. The AT
form
factor is found in older computers
(386 class or earlier). Some of the problems with
this form
factor mainly arose from the physical
size of the board,
which is 12" wide, often causing the board
to overlap with space required for the drive
bays.
Following the AT
form
factor, the Baby
AT form
factor was introduced. With the Baby
AT form
factor the width of the motherboard
was decreased from 12" to 8.5", limiting
problems associated with overlapping on the drive
bays' turf. Baby
AT became popular and was designed for
peripheral devices — such as the keyboard, mouse,
and video — to be contained on circuit boards
that were connected by way of expansion
slots on the motherboard.
Baby
AT was not without problems however. Computer
memory
itself advanced, and the Baby
AT form
factor had memory
sockets at the front of the motherboard.
As processors became larger, the Baby
AT form
factor did not allow for space to use a
combination of processor, heatsink, and fan. The ATX
form
factor was then designed to overcome
these issues.
ATX
-
With the need for a more integrated form
factor which defined standard
locations for the keyboard, mouse,
I/O,
and video connectors, in the mid 1990's the ATX
form
factor was introduced. The ATX
form
factor brought about many chances in
the computer.
Since the expansion
slots were put onto separate riser
cards that plugged into the motherboard,
the overall size of the computer
and its case was reduced. The ATX
form
factor specified changes to the motherboard,
along with the case and power
supply. Some of the design
specification improvements of the ATX
form
factor included a single 20-pin
connector for the power
supply, a power
supply to blow air into the case
instead of out for better air flow, less overlap
between the motherboard
and drive
bays, and integrated I/O
port
connectors soldered directly onto the motherboard.
The ATX
form
factor was an overall better design for
upgrading.
MicroATX
-
MicroATX
followed the ATX
form
factor and offered the same benefits
but improved the overall system
design costs through a reduction in the physical
size of the motherboard.
This was done by reducing the number of I/O
slots
supported on the board.
The MicroATX
form
factor also provided more I/O
space at the rear and reduced emissions from using
integrated I/O
connectors.
LPX
-
White ATX
is the most well-known and used form
factor, there is also a non-standard
proprietary
form
factor which falls under the name of LPX,
and Mini-LPX.
The LPX
form
factor is found in low-profile cases
(desktop model as opposed to a tower or
mini-tower) with a riser
card arrangement for expansion cards
where expansion boards
run parallel to the motherboard.
While this allows for smaller cases it also limits
the number of expansion
slots available. Most LPX
motherboards
have sound and video integrated onto the motherboard.
While this can make for a low-cost and space
saving product they are generally difficult to
repair due to a lack of space and overall non-standardization.
The LPX
form
factor is not suited to upgrading and
offer poor cooling.
NLX
-
Boards
based on the NLX
form
factor hit the market in the late
1990's. This "updated LPX"
form
factor offered support for larger memory
module,
tower cases, AGP
video support and reduced cable length. In
addition, motherboards
are easier to remove. The NLX
form
factor, unlike LPX
is an actual standard
which means there is more component options for
upgrading and repair.
Many systems
that were formerly designed to fit the LPX
form
factor are moving over to NLX.
The NLX
form
factor is well-suited to mass-market
retail PCs.
BTX
-
The BTX,
or Balanced Technology Extended form
factor, unlike its predecessors is not
an evolution of a previous form
factor but a total break away from the
popular and dominating ATX
form
factor. BTX
was developed to take advantage of technologies
such as Serial
ATA, USB
2.0, and PCI
Express. Changes to the layout with the
BTX
form
factor include better component
placement for back panel I/O
controllers
and it is smaller than MicroATX
systems.
The BTX
form
factor provides the industry push to
tower size systems
with an increased number of system
slots.
One of the most talked about
features of the BTX
form
factor is that it uses in-line airflow.
In the BTX
form
factor the memory
slots
and expansion
slots have switched places, allowing
the main components (processor,
chipset,
and graphics
controller)
to use the same airflow which reduces the number
of fans needed in the system;
thereby reducing noise. To assist in noise
reduction BTX
system
level acoustics have been improved by a reduced
air turbulence within the in-line airflow system.
Initially there will be three motherboards
offered in BTX
form
factor. The first, picoBTX will offer
four mounting holes and one expansion
slot, while micro-BTX
will hold seven mounting holes and four expansion
slots, and lastly, regularBTX will
offer 10 mounting holes and seven expansion
slots. The new BTX
form
factor design is incompatible with ATX,
with the exception of being able to use an ATX
power
supply with BTX
boards.
Today the industry accepts the ATX
form
factor as the standard,
however legacy AT
systems
are still widely in use. Since the BTX
form
factor design is incompatible with ATX,
only time will tell if it will overtake ATX
as the industry standard.