Hardware Reference
In-Depth Information
ITX and Mini-ITX
FlexATXdefinesaboardthatisupto9inches×7.5inches.AFlexATXboardcanbesmal-
ler 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
boardcouldbemadesmall enoughtouseonlyfourmountingholes(C,F,H,andJ).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 (0.25 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 con-
form 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%
smallerandyetstillconformedtotheFlexATXspecification.VIAcalledthisITXbutthen
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
widthanddepthdimensionsallowedbyFlexATX.ThecompanycalleditMini-ITX.Ines-
sence,allMini-ITXboardsaresimplyFlexATXboardsthatarelimitedtotheminimumal-
lowable 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,
