microATX Motherboard Interface Specification

Version 1.2

Page 9

2. Layout

This section describes the mechanical specification of the microATX form-factor motherboard, including

physical size, mounting hole placement, connector placement, and component height constraints.

2.1 Board Dimensions

Table 3 compares the microATX and ATX 2.1

board dimensions.

Table 3: microATX and ATX Board Dimensions

Dimension microATX board ATX board, full-sized

Maximum width allowable 9.6 inches (244 mm) 12 inches (305mm)

Maximum depth allowable 9.6 inches (244 mm) 9.6 inches (244mm)

2.2 Mounting Hole Placement

Table 4 describes motherboard mounting hole locations.

Table 4: Motherboard Mounting Hole Locations

Feature Status Comment

Motherboard mounting hole locations Required See Figure 2 for an overview and Figure 3 for exact locations.

Where possible, the microATX mounting holes line up with mounting holes used for ATX boards. Two new

holes (R and S in Figure 2) have been defined and added to provide mechanical support toward the front edge

of the microATX board.

• Figure 2 shows the relative outlines of the microATX and ATX boards. The letter callouts in the figure

show the general location of the mounting holes for both form factors. The table in the figure indicates

which holes are required for each form factor.

• Figure 3, the sample layout diagram, shows the exact location (dimensions) of the mounting holes for

microATX boards.

Chassis: To achieve full microATX compliance for chassis assemblies and to provide proper support for the

board in these areas, all nine microATX board mounting locations shown in Figure 2 should be implemented

in the chassis.

Motherboard: The board design can incorporate any combination of the microATX mounting holes shown

in Figure 2 if a given board design is smaller than the 9.6 x 9.6-inch maximum size. For a full-width

microATX board, hole R is required and hole S is optional. For a board that is narrower than 9.6 inches, of

the two new holes, R and S, only hole S is required.