Assignment #3

Motherboard Form Factors



Backplane




A circuit board containing sockets into which other circuit boards can be plugged in. In the context of PCs, the term backplane refers to the large circuit board that contains sockets for expansion cards.
Backplanes are often described as being either active or passive. Active backplanes contain, in addition to the sockets, logical circuitry that performs computing functions. In contrast, passive backplanes contain almost no computing circuitry.
Traditionally, most PCs have used active backplanes. Indeed, the terms motherboard and backplane have been synonymous. Recently, though, there has been a move toward passive backplanes, with the active components such as the CPU inserted on an additional card. Passive backplanes make it easier to repair faulty components and to upgrade to new components.

LPX


White ATX is the most well-known and used form factor, there is also a non-standard proprietary form factor which falls under the name of LPX, and Mini-LPX. The LPX form factor is found in low-profile cases (desktop model as opposed to a tower or mini-tower) with a riser card arrangement for expansion cards where expansion boards run parallel to the motherboard. While this allows for smaller cases it also limits the number of expansion slots available. Most LPX motherboards have sound and video integrated onto the motherboard. While this can make for a low-cost and space saving product they are generally difficult to repair due to a lack of space and overall non-standardization. The LPX form factor is not suited to upgrading and offer poor cooling.

NLX motherboard

New Low-Profile EXtended motherboard) A low-profile PC motherboard from Intel for slimline cases, introduced in 1987. Unlike boards for desktop and tower cases that hold the expansion cards perpendicular to the board, cards plug into a riser card on the NLX and are parallel with the board.

NLX is an industry-wide open specification for a space-saving computer motherboard. The NLX specification defines the motherboard size, hole mounting locations, riser card location, and maximum component heights on motherboard. Companies such as IBM, Hewlett-Packard, Digital Equipment, Sony, NEC, Toshiba, Gateway, and Fujitsu support NLX.
Traditionally a computer technician had to open the computer case using tools, but an NLX case is tool-free. Another feature of the NLX specification is the motherboard itself. It rests on rails and simply slides out without any screws to unscrew or card to remove. The motherboard plugs into a riser card that sits at a 90-degree angle from the motherboard. A riser card is an expansion card that physically extends a slot for more expansion cards. When the motherboard is removed, the riser card stays in place. This allows a technician to replace a motherboard or upgrade a component on the motherboard in about 30 minutes instead of the usual two hours, saving the customer money.
NLX motherboards support current and future processor technologies, the Accelerated Graphics Port (AGP), and tall memory technology. NLX is beneficial because it improves access to components, supports new technology, and lowers the cost of ownership.

ATX motherboard


The ATX (for Advanced Technology Extended) form factor was created by Intel in 1995. It was the first big change in computer case and motherboard design in many years. ATX overtook AT completely as the default form factor for new systems. ATX addressed many of the AT form factor's annoyances that had frustrated system builders. Other standards for smaller boards (including microATX, FlexATX and mini-ITX) usually keep the basic rear layout but reduce the size of the board and the number of expansion slot positions. In 2003, Intel announced the new BTX standard, intended as a replacement for ATX. As of January 2007 the ATX form factor remains the industry standard for do-it-yourselfers; BTX has however made inroads into pre-made systems, being adopted by computer makers like Dell, Gateway, and HP.
The official specifications were released by Intel in 1995, and have been revised numerous times since, the most recent being version 2.2[1], released in 2004.
A full size ATX board is 12" wide by 9.6" deep (305 mm x 244 mm). This allows many ATX form factor chassis to accept microATX boards as well.

AT motherboard


In 1985 IBM introduced Baby AT. Soon after all computer makers abandoned AT for the cheaper and smaller Baby AT, using it for computers from the 286 processors to the first Pentiums. These motherboards have similar mounting hole positions and the same eight card slot locations as those with the AT form factor, but are 2" (51 mm) narrower and marginally shorter. The size (220x330 mm) and flexibility of this kind of motherboard were the key to success of this format. While now obsolete, a few computers are still using it, and modern PC cases are generally backwards compatible to fit Baby AT.
In 1995, Intel introduced ATX, a modern 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 continued making Baby AT over ATX since many computer cases and power supplies in the industry were still compatible with 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 adapted to ATX specifications, it became common to design cases and power supplies to support both Baby AT and ATX motherboards.