Quad G4 Boards
su-geek writes " Synergy Microsystems offers QUAD G4 boards as well as QUAD G3 boards which all run SMP linux. Not only that but you can add more than one board to the dual PCI backplane." I didn't find any evidence of running Linux, and they don't appear to be motherboards: they look like addons, but still, they look nifty. I want a couple CPUs dedicated to running OpenGL screensavers in my root window or something.
Those things don't look like motherboards because they aren't. The VME and CompactPCI bus are industrial grade busses. The Synergy Micro boards are "Single Board Computers" that plug into a bus and control the boards that plug into other slots of the bus. These other boards can be anything from digital I/O for controlling machines, to video interfaces for machine vision applications. These systems go into applications for which your desktop PC (or Mac) would quickly fail. For example, my company is bidding on a project with a requirement that the boards in a CompactPCI (or is it VME, I forgot) withstand accelerations of 20G AND be able to survive being cleaned with a fire hose!