The layout of the board has been altered. The IO panel is moved down from the corner and the expansion slots to the other side where the IO panel on an ATX board would be. The CPU socket gets placed more central but closer to the edge of the board farthest fromt he rear of the case.
The idea is that a front fan, wind tunnel will feed air directly toward the CPU without obstruction. Theres a whole thermal unit thingy (technical term) that assists with this.
There are some good ideas, but whether the factor is successful and get's widespread adoption is far from decided. The specs have been around for years and we're just starting to see cases.
They reversed the order of the board for no reason whatsoever. Some cases will have the board mounted from the opposite side, to have the ports on top, others will have it on the "normal" side, placing the ports on the bottom.
The only reason Intel chose to reverse the board is to make sure you couldn't put a BTX board in an ATX case.
Intel came out with a new cooler design that relied completely on the case having a direct airflow path front to rear throught the CPU heatsink. They could have mandated that people use this design with ATX and called it ATX 3 or something, but that would have allowed people to find a workaround for older cases where the cooling would suffer. So instead they decided to toss everything and start anew, therefor ensuring that since the case would be totally new, it would have the correct airflow path.
And all this came about because Intel couldn't get the heat output of their latest P4's under control.
Buyers rebelled. Intel is even loosing business/server share to AMD now, partly due to performance but mainly due to power/heat issues.
So Intel is going back to basics. The Pentium M is based on the P3, but with modern optimizations. It uses around 1/4 the power of equal performance P4's, and therefor produces around 1/4 the heat. New desktop processors will be based on the Pentium M design.
So you could say that BTX was designed for the latest P4, but that by the time it gets any wide acceptance the processor it was designed for will already be off the market! In other words, BTX is pointless.
BTX does have cooling advantages, but the types of advantages seen here are not needed for cooler processors.
This is a bit off topic, but in the article about atx and btx cases they state that "While the X-Blade unit isn't available outside Europe, the ASYS case is available worldwide" I would just like to correct the author that x-blade cases are available outside europe, it seems that every second pc owner in this country owns one, even though they are rather, um.... (i do not wish to be banned on my first post). X blade cases are on sale in South Africa everywhere (I think we possibly fall under Europe as far as computer parts are concerned(just add a few hundred dollars, rand, pounds or euro extra to everything's price tag.)).