So, out of mere curiosity, I've taken to doing a bit of research on the PICMG 1.0 based single board computer stuff, and, if the prices weren't absolutely outrageous, it would be a bit interesting to have, more or less, fully modular CPU/chipset combos in one machine that we could switch out to solve speed issues/have faster that usual CPUs with ISA hardware.

Now this has certain disadvantages:
You're not going to mix PCI-E and ISA, ever it seems

No AGP support, with the only exception being an SBC that has a 'mini' AGP card slot on it, so only AGP cards made for a very little, and generally portable, uses, hard to find cards for, interface.

Due to the 'backplane' nature of these boards, I have a feeling that I/O bus saturation may be very, very easy to cause, probably limiting the usefulness of them.

Cost. Around $200 for a given SBC. At least backplanes are <100

That said, the CPU ranges are absolutely insane, ranging from 486s
http://www.ebay.com/itm/AAEON-SBC-492-full-si … =item3f17f7974a
to early Core 2 CPUs.
http://www.ebay.com/itm/Advantech-PCA-6194G2- … =item2ec0eba59f
and if you're willing to drop the PCI support, then you can go as low as a 386SX.

Even some exotic stuff, like Socket 8, Dual Slot 1, dual socket 370 w/ 440BX, dual socket 601, and some Geode and other specialized embedded x86 stuff, like this one 486 compatible that took DDR, that I saw, that would be interesting to play with.

The backplanes usually give favorable amounts of expansion.
http://www.ebay.com/itm/ICS-PCI-14p12-15-slot … =item5d36e9ed7b
http://www.ebay.com/itm/Portwell-pbp-14A7-14- … =item41702a7fab
So, there is that advantage.

Has anyone attempted to do a build with SBC/PICMG hardware? Or was the cost too much to justify it?