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A number of standard and proprietary form factors have evolved for motherboards in personal computers, some more successful than others. In an attempt to reduce the space requirements of computer systems, Western Digital introduced their proprietary Low Profile eXtension (LPX) form factor in the early 1990s. The format relied on the use of a riser board, mounted at right-angles to the main circuit board, which housed one or more expansion slots. Add-on cards were thus mounted parallel to the main board, allowing the size of the case to be reduced significantly.

The Balanced Technology eXtended (BTX) form factor was proposed by Intel in 2004 as the successor to the popular ATX format, and introduced a number of new features including changes to the layout of the board designed to improve component placement, enhancing airflow inside the case and reducing the number of cooling fans needed (which has the additional benefit of making the system run more quietly). Unfortunately, the layout makes the format incompatible with processors that require a specific orientation relative to the board's memory slots. Whether because of this or for other reasons, the BTX form factor has never attained the popularity enjoyed by ATX and its variants, which continue to dominate the market. Whereas the popularity of the ATX format has ensured that there are a wide range of compatible and competitively priced products available for it, standardised and inexpensive components for BTX systems are comparatively hard to find. In addition, advances in processor technology have resulted in processors that are more compact and generate less heat than has previously been the case. This has reduced the need for the kind of improvements in airflow that BTX was designed to bring about. Intel themselves ceased development of BTX products as of 2006.

Although popular with OEMs for a few years, LPX had a number of limitations. The number of expansion slots was limited, the system was difficult to upgrade or repair due to its proprietary format and the low availability of compatible parts, and poor airflow inside the chassis could lead to cooling problems. The format was revised by Intel and standardised in the shape of the New Low-Profile eXtended (NLX) form factor in 1997. Changes included improved options for upgrades and repairs and a design that placed an emphasis on ease of maintenance. Although a number of NLX-based computers were produced in the late 1990s, the design did not enjoy the same success as its predecessor. A number of major PC manufacturers instead chose to use emerging form factors such as the Micro-ATX, or produced their own proprietary solutions for low-profile and low cost systems.

Layout of a typical ATX motherboard ->

The Motherboard ~ Part #2

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