ATX form factor

The Intel Advanced/ML motherboard, launched in 1996, was designed to solve issues of space and airflow that the Pentium II and AGP graphics cards had caused the preceding LPX form factor. As the first major innovation in form factors in years, it marked the beginning of a new era in motherboard design. Its size and layout are completely different to the BAT format, following a new scheme known as ATX. The dimensions of a standard ATX board are 12in wide by 9.6in long; the mini ATX variant is typically of the order 11.2in by 8.2in. The ATX design gets round the space and airflow problems by moving the CPU socket and the voltage regulator to the right-hand side of the expansion bus. Room is made for the CPU by making the card slightly wider, and shrinking or integrating components such as the Flash BIOS, I/O logic and keyboard controller. This means the board need only be half as deep as a full size Baby AT, and there’s no obstruction whatsoever to the six expansion slots (two ISA, one ISA/PCI, three PCI). An important innovation was the new specification of power supply for the ATX that can be powered on or off by a signal from the motherboard. At a time when energy conservation was becoming a major issue, this allows notebook-style power management and software-controlled shutdown and power-up. A 3.3V output is also provided directly from the power supply. Accessibility of the processor and memory modules is improved dramatically, and relocation of the peripheral connectors allows shorter cables to be used. This also helps reduce electromagnetic interference. The ATX...

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