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[ The PC Guide | Systems and Components Reference Guide | Power | The Power Supply | Power Supply Form Factors ]

WTX Form Factor

If the SFX form factor is the little brother to ATX, WTX isn't quite its big brother. WTX is more like its overgrown third cousin from a distant country. :^) Introduced by Intel (who else) in 1998, and revised in 1999, the WTX form factor is designed specifically for workstations (thus the "W" in "WTX"). WTX defines a standard for motherboards, cases, and power supplies.

To meet the increased needs of the largest regular PC systems, the WTX form factor is totally different from the other PC form factors. It is designed in a modular way from the ground up to allow it to meet the needs of large, multiple-CPU systems now and in the future. The system is segmented physically into different "zones" where different functions are supposed to be incorporated into the system. The motherboard is mounted on a special mounting plate which gives motherboard makers the flexibility to design boards without "hard-coded" mounting hole restrictions. For its part, the power supply has been completely changed to suit the needs of these larger systems. The best way to really understand the WTX form factor is to download and read the specifications that are available at the WTX Home Page.

Unsurprisingly, WTX power supplies are large and powerful. The WTX specification actually includes design guides for three specific sizes of power supply: 460 W, 610 W, and a whopping 800 W, though manufacturers are not limited to those particular numbers. For designs up to about 500 W, a single power supply fan is specified, with overall power supply dimensions of 150 mm width x 230 mm depth x 86 mm height. For larger capacity supplies, a dual-fan configuration is recommended, which increases the width of the package to 224 mm.

Top and rear view diagrams of a dual-fan configuration
WTX form factor power supply.

Created using elements from an original image PC Power & Cooling, Inc.
Image used with permission.

The motherboard connectors used for the WTX are completely different from, though similar in concept, those of ATX and SFX. Two large connectors with a total of 46 pins (6 reserved for future use) are the main connection to the WTX motherboard (or set of boards) Several additional connectors are also optional for powering additional CPUs or other devices. The WTX power supply also supplies several extra signals unique to the WTX form factor. WTX supplies are intended to be matched to WTX motherboards and put in WTX form factor cases. They normally include a large number of drive connectors to run a large number of hard disk drives and other devices, or special wiring to accomodate RAID bays.

Next: Comparison of Power Supply Form Factors

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