I just finished testing my new Mach 3 driven Atom PC. It works great!
I've been using a standard PC, Derek's (Hillbilly) breakout board, and Mach 3 on my mill for sometime. Last month my PC took and dive so I decided to try something different. Previously, I had the PC mounted in the side cabinet and I noticed a lot of vibration during heavy machining. PC circuit boards do not like this and indeed my motherboard is what ended up failing.
The Atom motherboard is only 7 x 8 inches. I have an ASUS AT3GC-I. My total enclosure size with hard drive and CD ROM is only 5 x 9 x 13 inches. I got all of the stuff online. The MB, Case and RAM only cost $190. I used the old hard drive and CD ROM.
In the photos you can see that I have a bracket on the side of the mill that contains the PC box and a mount for the monitor. The monitor mount is adjustable. I also have a swiveling pan for the keyboard.
Hopefully someone gets an idea from this for their own MOD!