Sidebar: Motherboard Form Factors

Motherboards exemplify what is perhaps the most rigorous application of form factors. Here, form factor describes a specification that includes the overall length and width of the board, the arrangement of attachment holes and the placement of I/O ports and slots for add-in cards (whether AGP, PCI or SCSI). The form factor also defines board component height-restriction zones and mounting holes -- elements that interface with the chassis and power supply.

The most common motherboard form factor today is called ATX. Introduced by Intel Corp. in 1995 as an extension of the Baby AT form factor, ATX motherboards have a maximum size of 12 by 9.6 in. Smaller variants include the MiniATX, MicroATX and FlexATX. The less common EATX (Extended ATX) will likely be superseded by a new WTX form factor designed especially for workstations.

The newest motherboard form factor, Intel's BTX (Balanced Technology Extended), was announced last fall but isn't on the market yet; products should arrive later this year, however. BTX is mechanically similar to ATX but represents a technological update, allowing newer memory types, better thermal handling, faster storage (Serial ATA) and component (PCI-X) interfaces, two different heights (standard and low-profile) for components, and a greater range of board sizes.

Kay is a Computerworld contributing writer in Worcester, Mass. You can contact him at russkay@charter.net.

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