BTX Motherboards

Red Herring Article on Nisvara

Intel Architecture Programming and CPU information

Slashdot discussion on BTX formfactor

ATX Form Factor stands for "Advanced Technology eXtended"
EATX Form Factor stands for "Extended ATX"
BTX Form Factor stands for "Balanced Technology eXtended" the newest formfactor for reducing noise with increased cooling

Intel has been working on a new form factor, code-named Big Water, for well over a year now. It's now officially called "BTX" . The key goals of BTX are to create a form factor that facilitates the cooling of increasingly hot CPUs and minimizing the acoustic impact of a wintel PC.

One key feature of BTX is how the air is circulated through the system. Air is sucked in through a single, large case fan (typically 120mm), which rotates relatively slowly. One of the interesting aspects of the fan construction is the fan shroud. In the past, the fan shroud has simply been a box around the rotating impeller. But Intel's mechanical and fluid dynamics engineers have created a stator, which is a fixed shroud that looks something like the fan itself, but doesn't rotate. The stator has one more blade than the impeller, and is designed to reroute the airflow from the fan in a more coherent way, as well as minimize fan noise.

The rear case fan also acts as the CPU cooling fan, routing cool air through a duct, over a passive, finned heatsink atop the CPU itself. The air then circulates past the CPU through the rest of the system. The graphics hardware is also in the primary circulation path.

BTX layout

Here's one prototype of a compact BTX case, with the fan and fan duct visible. Towards the back of the picture (the front of the case), you can see a full-height graphics card (PCI Express, of course) mounted sideways.

PDF of the BTX formfactor specification

Overview of BTX Case

Cad Drawing of BTX Silent Fan

Closeup view of BTX fan assembly

Closeup view of dismanted BTX fan assembly

Flomerics Thermal Simulation of heat and airflow for BTX chassis

Overview of Family of BTX motherboards, PicoBTX, and MicroBTX form factors