-Now most of you may have looked around and you have seen an ATX or AT form factor. Most of the time this will be marked on the motherboard or the case itself. You want to make sure these two are the same when shopping. The main form factors to worry about are the AT and the ATX. What's the difference in these factors? Basically the AT is the old conventional standard with the ATX being the new and improved version.
-AT and Baby AT, This is an old IBM design that is still widely used today. There are however some drawbacks to the case. When trying to construct a computer with a AT case you will have very little space and and uncomfortable environment for the system components. The power supplies on these cases are also bad about ventilating the case due to that the fan pulls hot air out of case rather than push cool air in case like the ATX design. Now on the good side of the AT is they are really cheap now and most of the manufacturers are liquidating stock. Best advice on this case is stay away from it if at all possible. The ATX is a better design and will carry us far into the future.
-ATX, this design brings many things that were missed in the AT form factor. The ATX is basically a throw off of the Baby AT format. This allows the motherboard to be installed at a 90° rotation. Something else about the ATX is ventilation. The power supply pulls in cool air and pushes it our through vents in the case. This really seems to help with dust build up in the computer. My most recent machine uses the ATX case and its so much better. Not only are the ATX better but more versatile for expansion slots, power management, no excess ribbon cables, allowing more integration on the motherboard. Best advice is buy a ATX case.
