Posted on January 19, 2004
My seven year old 200 MHz Pentium class PC was showing its age last year. The mini-ITX boards were perfect for a new computer, well suited for running 24x7 due to relatively low power requirements. They also had ample I/O ports, both USB and Firewire as well as serial and parallel ports. Linux support was still partial then but sufficient for my uses. As it has turned out, most of the hardware devices on the M class EPIA boards have at least alpha or beta quality driver support now under Linux. It is a pleasant surprise to see how well Linux is able to handle decoding video streams (compared to a few years ago when it was crippled). I am running a 2.4.22 kernel with glibc 2.3.2 (patched to avoid cmov bug in glibc), gcc 3.3.2, XFree 18.104.22.1682 and MPlayer 1.0pre2.
The real reason I elected to use a mini-ITX mainboard was its very small size. It was just cool and offered more possibilities for case design. I wanted to build something unique that could fit in a bookshelf. I'm happy with the result although the project has evolved over time. There were never any fixed plans so the computer didn't turn out how I originally envisioned it. A coworker referred to it as the "Borg Appliance" which seemed most appropriate given the organic nature of Borg technology.
A year ago, I set up a small machine shop in my 600 square foot apartment bedroom to remedy a foolish mistake when over tightening a machine screw. I didn't want to pay a machinist or smith to do the job so decided to set up my own shop which would be useful for many things. I had no experience with machine tools or metalwork. I also didn't have a workbench or table so had to make that first. Below you can see the milling machine on the worktable with some of the aluminum chip aftermath from this project. Fabrication went on for months in spare time after work. To give an idea of how much time it takes, the recessed holes for the USB and Firewire ports in the front aluminum panel took nine hours to mill. All of the polycarbonate panels were cut, drilled, tapped, and fitted, with hand tools in about 100 hours. It would have been a lot easier and faster if the mill were larger and I had proper power tools for cutting plastic.
The Borg Appliance has a frame of milled 6061-T6 aluminum stock held together with alloy socket head machine screws. The case panels are .093 Lexan (polycarbonate). There are a lot of close fitting parts, particularly the tongue and groove joints between the columns and rails that together with the front and rear panels form the frame of the case. I learned a lot about milling aluminum and working polycarbonate from this project.
All of the electronics came from a local store in Dallas: a VIA M9000 mainboard, 512 MB DDR, 180 Watt power supply, 180 GB hard disk, two snap switches and wire. The aluminum stock and most of the machine screws came via mail order from ENCO, an industrial supply company. The metric screws for mounting the USB/Firewire header plugs came from Elliot's Hardware. The polycarbonate sheet and rubber washers (used for faucets) came from a Home Depot down the street.
Assembly is somewhat involved, more like working on an automobile in that you have to put things together in the correct order. The front and rear aluminum panels are screwed into the thick columns with countersunk 8x32 screws. The power plug is a snug fit in the front panel. The hole for the plug was roughed out with a quarter inch end mill and then fitting done by hand with a mill file. The snap switches (upper one is power, below that is reset) are epoxied in place.
At first, the hard disk mounting rails were plain quarter inch thick aluminum rectangles. Unfortunately, to get the master power switch on the front panel to fit in place, the hard disk had to move another one eighth inch outwards. So I had to mill out a recess in the rails. The finish looks different in the recess as I used a mill file to do the final fitting by hand.