ATX vs Micro ATX
When buying computers, most people do not know that there are two common form factors for desktops; the ATX and Micro ATX, which is also commonly abbreviated as mATX or uATX. “ATX” stands for “Advanced Technology eXtended” and was an improved version of the older AT form factor. Micro ATX is one of the offshoots of ATX, and its main difference from the main ATX form factor is size. ATX retains a generally rectangular board size measuring 305mm. by 244mm. Micro ATX is a more even square which retains the 244mm. width but cuts down the length to by 61mm.
The main downside of Micro ATX compared to ATX is the reduced number of expansion ports that are located on the bottom end. While ATX boards typically have five expansion slots, Micro ATX typically has three with four being the absolute maximum. This is partially offset by many board manufacturers integrating common functions like sound, networking, and even graphics. It is no longer uncommon to see computers that do not utilize the expansion ports.
Even though Micro ATX is a smaller form factor, the identical width allowed it to retain most of the mounting points established by the ATX form factor. This allows Micro ATX boards to fit and mount perfectly inside an ATX chassis. With Micro ATX cases, the main focus is a reduced size for a smaller footprint. This inhibits the use of an ATX board inside a Micro ATX chassis.
An indirect consequence of the Micro ATX form factor is the reduced number of drive bays inside the case. Not much of a problem if you only have one or two hard drives inside, but it can be an issue if you have a lot of hard and optical drives or you want to implement a RAID. For many, more room is generally better to accommodate future expansions even if they never really do it. Because of this, Micro ATX cases are still not as popular even if Micro ATX motherboards are now more popular than the full-sized ATX boards.
Summary:
1.ATX is larger than Micro ATX.
2.ATX boards typically have more expansion slots than Micro ATX boards.
3.A Micro ATX board can be installed in an ATX chassis but not the other way around.
4.A Micro ATX chassis has fewer drive bays than an ATX chassis.