According to PCMag, the Advanced Technology Extended motherboard (ATX) was the first PC motherboard to not only include I/O support (serial, parallel, mouse, etc.) but also to place all the connectors directly on the motherboard. Balance technology extended (BTX) is a form factor for motherboards that were initially intended to replace the 2004 and 2005 ATX motherboard.
The ATX motherboard is still one of most commonly found and used motherboards. ATX is an Intel trademark first created and released in July 1995 and has been revised several times since then. The ATX motherboard is 12 inches by 9.6 inches and has the COM, LPT, PS/2 and USB ports mounted directly on the motherboard. Numerous variations of the ATX were subsequently introduced with both smaller and larger form factors, including the microATX, Mini ATX, FlexATX and Extended ATX.
The BTX form factor is a scalable form factor that allows for a wide range of system sizes and profiles. There are several benefits associated with a properly designed BTX system over designs from previous form factor specification generations. These benefits include scalability in system design, improvements to system power delivery and power dissipation, acoustics, board layout and routing, high-volume manufacturing costs and structural integrity.