Clearly, I have lost my mind. In a moment of boredom so sublime as to be worthy of song, I took an idea from this thread... http://forums.offtopic.com/showthread.php?t=2309525 ...and started looking around for what parts I would need to take a couple of older Pentium 4s that I have and build a usable dual-CPU computer out of it. This is not a practical idea. I'm not trying to save money. This is about doing something I haven't done 50 times before. So, my question is, has anybody ever built a functioning computer using more than one Single-Board Computer and a backplane module to connect them with? If so, could someone please explain to me, in general, how the hell these two supposedly separate computers manage to synchronize their activities? Furthermore, could it possibly run Windows without having to hack things to bits and put them back together again? EDIT: Are conventional dual-CPU motherboards built the same way, just completely integrated onto a single circuit board? If so, that would ease my mind a bit.