I finally got a few sample VIA Eden boards, and they do look pretty interesting for Linuxbios. I havent installed one yet, so I dont know what the hardware is like (or performance...), but they are only a little larger than the Advantech 5823 or other 3.5 inch machines, support 1GB RAM, and a PCI slot (I will test the GiGE throughput shortly...).
Hopefully VIA will be a bit more forthcoming about docs for this as it is for embedded systems. There is supposed to be a release with on board DoC but mine dont. They are very cheap. About 76 of our British pounds, so probably $100. They are 4U square, so you could probably get 2 rows of 6 in a 4U case if you put them vertically (you could use a right angle PCI connector if you need the card). Justin
