This design should benefit video card manufacturers greatly. Previously, they could not count on any outside airflow being passed over the fronts of videocards, seeing as how PCI Express video cards face away from the processor and system fans in ATX cases.

The motherboard chipsets (Northbridge and Southbridge) have also had their locations formalized in the middle of the motherboard, in-line with the thermal module's stream of air. They are next in line after the processor to receive fresh air from the front vent, with the idea that the can be passively cooled with the CPU heatsink exhaust air stream.

System memory has been placed where the PCI Express/AGP slot would reside in ATX designs; slightly below (left of) the center of the board and the air stream provided by the thermal module. To aid in air circulation, the memory slots travel in the same direction as the airflow (front to back). Though they are slightly out of the main flow of air, the memory modules should receive cooling since the power supply will pull some air across them with its exhaust fan. RAM cooling is not a major factor in current systems, so no real focus has been given to it in BTX.

Interestingly, the BTX form-factor also provides for airflow under the motherboard. Part of the air pulled in by the thermal module will be directed on the same line underneath the board, cooling as it goes. This can potentially help in the thermal regulation of several essential system components, not the least of which being the CPU socket, MOSFET's, and BGA chipsets. To enable this, the motherboard will obviously sit further away from the floor or wall of the case than it has in the past.

BTX Case Changes

Several changes to computer case layouts have also had to be made to accommodate the new BTX motherboard form-factor. I/O and expansion ports are now in different locations on the back of the case, and each BTX case must have a 'thermal module interface' at the front.

The thermal module interface is the vent that provides outside air directly to the thermal module, and must be engineered so that the vent and the thermal module fit precisely. This is to prevent air from inside the case being recycled. An equivalent exhaust vent must also be present at the rear of the case, both above and below the motherboard plane according to Intel documents.

A few companies have already released one or two different BTX tower cases, but demand for these full-size cases is likely to be slow for most of 2005. The BTX case appears identical to a standard ATX case, except that the motherboard tray is on the left wall of the case, rather than the right as ATX cases do. This enables the peripheral and I/O ports to be more or less in the position that most people are familiar with despite its relocation on the actual BTX motherboards.

Acoustical Considerations

Intel appears to have gone to a lot of trouble to ensure that the thermal module will not recycle heated air from inside the case when cooling the CPU. The front thermal module interface links to the thermal module via a gasket, and its stream of air is vented out the rear of the case only, ensuring a steady flow of new air. On paper, it's hard to see how this could fail to cool modern processors and chipsets well, as compared to the current, rather haphazard ATX design. The proof will be in the testing though.

A single 90mm fan should be good news for folks who like quiet systems. The fan will vary between 900 and 4500 RPM depending on system temperature (as judged by the CPU temperature as well as a sensor placed on the motherboard right in the primary air flow). Looks like Intel's version of AMD's 'cool n' quiet' tech is finally here. It'll be interesting to see how much noise a BTX system really generates excluding the video card fan when they finally reach the PCstats labs.