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Author Topic: AT & BABY-AT Form Factors  (Read 2135 times)

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Offline chrisNova777

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AT & BABY-AT Form Factors
« on: September 18, 2017, 11:22:57 AM »
Quote
The "new" IBM PC/AT didn't look all that much different on the outside from the PC/XT units it replaced; but on the inside it was a different story. The AT case was functionally similar the older PC/XT style, but was changed slightly so that it represents a different form factor. The power supply was larger than in the PC/XT and the positioning and size of the motherboard and power supply different. Therefore, the PC/XT and AT formats were not compatible.

The AT form factor was very popular in the late 1980s, and was the basis of many "clone" manufacturers' units (for compatibility with IBM.) The AT system was also the first to formally introduce different desktop and tower configurations, as described on this page discussing the AT form factor power supply.

The desktop configuration was very similar to that of the PC/XT, with the familiar red toggle switch in the rear of the machine, on the right-hand side. The tower configuration saw the introduction of the now familiar "remote" power switch, controlled by a button on the front of the case. Due to its convenience, this was very popular and became the standard for most later designs, both tower and desktop.

http://www.pcguide.com/ref/case/form.htm

https://en.wikipedia.org/wiki/AT_(form_factor)
Quote
In 1985 IBM introduced Baby AT and soon after all computer makers abandoned AT for the cheaper and smaller Baby AT form factor, using it for computers that spanned several generations, from those that used 286 processors to the P5 Pentium and a limited number of Pentium II systems. These motherboards have similar mounting hole positions and the same eight card slot locations as those with the AT form factor, but are 2 inches (51 mm) narrower and marginally shorter. The size 13 × 8.5 in (330 × 216 mm) and flexibility of this kind of motherboard were the key to success of this format. The development of bigger CPU coolers—and the fact that they blocked full-length PCI and ISA cards—spelled the end of Baby AT and was the main impetus for its successor ATX. While the AT standard is now considered to be mostly obsolete, some industrial computers still use it.

In 1995, Intel introduced ATX, a form factor which gradually replaced older Baby AT motherboards. During the late 1990s, a great majority of boards were either Baby AT or ATX. Many motherboard manufacturers favored Baby AT over ATX as many computer cases and power supplies in the industry were still designed for AT boards and not ATX boards. Also, the lack of an eighth slot on ATX motherboards kept it from being used in some servers. After the industry shifted to ATX motherboard configurations, it became common to design cases and power supplies to support both Baby AT and ATX motherboards.


Offline chrisNova777

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