Hardware Reference
In-Depth Information
ITX and Mini-ITX
FlexATX defines a board that is up to 9 inches × 7.5 inches. A FlexATX board can be smaller than
that, but how much smaller? By analyzing the FlexATX specification—and, in particular, studying the
required mounting screw locations—you can see that a FlexATX board could be made small enough
to use only four mounting holes (C, F, H, and J). Refer to
Figure 4.16
for the respective hole
locations.
According to the FlexATX standard, the distance between holes H and J is 6.2 inches, and the
distance between hole J and the right edge of the board is 0.25 inches. By leaving the same margin
from hole H to the left edge, you could make a board with a minimum width of 6.7 inches (0.2
5 inches
+ 6.2 inches + 0.25 inches) that would conform to the FlexATX specification. Similarly, the distance
between holes C and H is 6.1 inches, and the distance between hole C and the back edge of the board
is 0.4 inches. By leaving a minimum 0.2-inch margin from hole H to the front edge, you could make a
board with a minimum depth of 6.7 inches (0.4 inches + 6.1 inches + 0.2 inches) that would conform
to the FlexATX specification. By combining the minimum width and depth, you can see that the
minimum board size that would conform to the FlexATX specification is 6.7 inches × 6.7 inches
(170mm × 170mm).
VIA Technologies Platform Solutions Division wanted to create a motherboard as small as possible,
yet not define a completely new and incompatible form factor. To accomplish this, in March 2001
VIA created a board that was slightly narrower in width (8.5 inches instead of 9 inches) but still the
same depth as FlexATX, resulting in a board that was 6% smaller and yet still conformed to the
FlexATX specification. VIA called this ITX but then realized that the size savings were simply too
small to justify developing it further, so it was discontinued before any products were released.
In April 2002, VIA created an even smaller board that featured the absolute minimum width and depth
dimensions allowed by FlexATX. The company called it Mini-ITX. In essence, all Mini-ITX boards
are simply FlexATX boards that are limited to the minimum allowable dimensions. All other aspects,
including the I/O aperture size and location, screw hole locations, and power supply connections, are
pure FlexATX. A Mini-ITX board fits in any chassis that accepts a FlexATX board; however, larger
boards will not fit into a Mini-ITX chassis.
The Mini-ITX form factor was designed by VIA especially to support VIA's low-power embedded
Eden ESP and C3 E-Series processors. However, third-party vendors have also adopted this form
factor for use with low-power netbook-class chips such as Intel's Atom and AMD's E- and C-series,
as well as with more powerful processors such as Intel's Core i3 or Core i5, and AMD's Phenom,
Athlon 64 X2, Athlon 64, Athlon II, Phenom II, or Sempron 100. Mini-ITX systems that use these
processors can be used as multimedia servers and small form factor PCs as well as for set-top boxes
and computing appliances.
The size of the DTX and ITX families of motherboards as they relate to FlexATX is shown in
Table
