AMD DTX small form factor system preview

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October 22, 2007 by Mike Chin

The setting of standards and form factors in the PC industry has largely been the domain of Intel for so long that it's hard to remember when things were different. When things were different, all the way back in the early 90s and before, portions of the PC industry were in chaos as various standards for all kinds of components — graphics card slots, for example — competed for dominance. Compatibility is the glue that allows companies in the PC industry to work and thrive together; the role of widely-accepted standards is critical in achieving compatibility. Although broad consensus is required for successful establishment of industry standards, Intel has been the major driving force in this area for some time.

The development of the DTX spec was announced by AMD last January.
The photo above shows a reference design.

So last January's announcement of the development of DTX, an open standard specification designed by AMD to enable the broad adoption of small form factor PCs, came as a bit of a surprise to many. The gist of DTX is contained in the following extract from AMD's presentation.

More information is available at DTX Form Factors, including a Reference Design Overview Slideshow, an FAQ, and a DTX Mechanical Interface Specification. As we go to press, some 70 vendors have registered to implement DTX, and the list includes most of the biggest names in the PC component business.

The short 10-page DTX Mechanical Interface Specification is focused almost entirely on motherboard form factors; there's virtually nothing on cases or power supplies. The emphasis on broad compatibility with existing specifications is strong:

  • DTX motherboard size and mounting specifications are designed to be compatible with existing ATX and Micro ATX chassis specifications.
  • Mini-ITX motherboard size specifications are compatible with DTX chassis specifications.
  • The general DTX specification defines a minimum set of parameters necessary for interoperability, freeing vendors to innovate.

This emphasis on compatibility is not surprising. DTX is more or less and extension of ATX. Obviously, AMD wants to avoid what happened to BTX.

Intel tried to roll out BTX a few years ago with three sizes: full BTX, micro MTX and pico BTX to replace not only ATX and micro-ATX, but also set a new SFF form factor. Part of the impetus was to introduce a different system airflow design that could deal more effectively than ATX with the thermal problems of Intel's hot Pentium 4 (Prescott and later) processors. BTX was not compatible with ATX cases or power supplies, however, which meant manufacturers had to use not only a new motherboard form factor, but entirely new types of cases and power supplies to adopt BTX.

This was probably the major reason that BTX did not gain wide support. It appears to be used today only by a few major Intel partners. Certainly, it's just about impossible to find a BTX motherboard, case or power supply for sale in the retail component marketplace. (You can find BTX information at Intel's Form Factors web site.)

In case you haven't guessed yet, the name DTX naturally follows from ATX and BTX... although perhaps an inquiry should be made about what happened to CTX?

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