ATX (Advanced Technology eXtended) and NLX (New Low Profile eXtended) are two computer form factors that determine motherboard specifications. The ATX form factor is more commonly used, whereas the NLX form factor is typically used in smaller cases. ATX motherboards are 12 inches wide and 9.6 inches deep, while NLX motherboards are typically 10 inches wide and 8 inches deep.
The biggest factor that differentiates NLX from ATX is the presence of the riser board that allows NLX motherboards to add two to four expansion cards. It also lets the user remove the motherboard from the computer without having to remove the expansion cards without the use of any tools. Also, ATX motherboards feature expansion slots that are located on the motherboard itself.
The ATX form factor was introduced by Intel in 1995 and has remained popular as of 2014, while NLX motherboards, which were introduced in 1997, were eventually replaced by motherboards featuring the FlexATX, Micro-ATX and Mini-ITX form factors.
The number of expansion slots that standard ATX form factors provide is capped at seven, while the number of slots provided by NLX form factors varies. One of the main advantages of NLX is its size, which allows a user to place a server into a VCR-sized case, whereas ATX offers users advanced power management features.