Motherboards and Buses - Upgrading and Repairing PCs - page 169

Figure 4.18. Size and mounting hole comparison between ATX, microATX, and FlexATX
motherboards.
Most FlexATX systems use SFX/TFX (small or thin form factor) type power supplies (introduced in
the microATX specification), although if the chassis allows it, a standard ATX power supply can be
used.
The addition of FlexATX gave the family of ATX boards four definitions of size (three are the
official standards), as shown in Table 4.4 .
Table 4.4. ATX Motherboard Form Factors
Note that these dimensions are the maximums allowed. Making a board smaller in any given
dimension is always possible as long as it conforms to the mounting hole and connector placement
requirements detailed in the respective specifications. Each board has the same basic screw hole and
connector placement requirements, so if you have a case that fits a full-size ATX board, you could
also mount a microATX or FlexATX board in that same case. Obviously, if you have a smaller case
designed for microATX or FlexATX, you can't put the larger Mini-ATX or full-size ATX boards in
that case.
DTX and Mini-DTX