The ATX and the BTX -- acronyms for Advanced Technology eXtended and Balanced Technology eXtended, respectively -- are motherboard form factors that the semiconductor company introduced in 1995 and 2003, respectively. Both standards specify the size and design of a motherboard, which acts as the heart of the personal computer since it contains many of its key components. The BTX never caught on as the replacement for the ATX. However, it was designed as an advancement over its predecessor, judging by the differences between the motherboard form factors.
Size
In terms of size, the ATX motherboard form factor has two variants: the regular ATX, which measures 12 inches wide and 9.6 inches deep, or 305 by 244 millimeters; and the smaller version called microATX, which is 9.6 by 9.6 inches, or 244 by 244 mm. The BTX motherboard has three main variants: the original BTX, which is 12.8 by 10.5 inches, or 325 by 266 mm; microBTX, which is 10.4 by 10.5 inches, or 264 by 267 mm; and the picoBTX, which is 10.5 by 8 inches, or about 268 by 203 mm. Regardless of size, the BTX is larger than the ATX.
Processor and System Memory
Each ATX and BTX motherboard has a section for placing a processor, or central processing unit. This component is physically and electrically connected to the motherboard using its CPU socket, and is accompanied by a fan for its cooling system. The CPU is placed at the ATX's upper middle section, while that of the BTX goes at the lower middle section. Also included are dual inline memory module (DIMM) slots: up to four for the ATX, two for the BTX.
Disk Drives
The ATX and the BTX motherboard have connectors for accommodating disk drives: namely hard disk drive for data storage space, optical disc drive for playing discs such as CDs and DVDs, and floppy drive for inserting floppy disks. The ATX provides support for three disk drive connectors and two drive bays. The HTX can provide support for up to two optical disc drives, and a hard drive and floppy drive.
Expansion Ports
The expansion ports on each ATX and BTX motherboard -- which include Peripheral Component Interconnect (PCI) interfaces and Accelerated Graphics Ports (AGPs) -- serve as slots for enhancing the computer with cards such as discrete video/graphics cards, wireless network cards and sound cards. The ATX and BTX form factor can offer up to seven expansion ports, with the number often depending on size. For instance, the micro versions of the ATX and the BTX have four and the picoBTX has one.
Inputs/Outputs
The inputs/outputs -- usually abbreviated as I/Os -- is a reference to the audio/video and networking connectors that the ATX and BTX motherboard form factors provide. This includes USB ports; headphone and microphone jacks; Ethernet, or RJ-45 jack for wireless networking; PS/2 for connecting the computer keyboard and mouse; and Video Graphics Array (VGA) port for hooking up the computer monitor. The I/O section is placed at the ATX's upper middle section, right next to the processor. The BTX offers front panel I/Os as well, although it adds back-panel ones on the traditional desktop tower.
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