I've got the cable you're talking about, was that intended for mirroring to a projector in schools? That was my understanding. In auctions, I've only seen them installed in 5XXX AIOs. Interesting, the little LC Slot portion of the Apple PC Compatibility Cards cable to that MoBo connector and to the Processor portion of the card, which funnels PC video(?) to it. The Reply double-decker setup uses an edge to edge PCB to bridge the connection to the top board while the bottom board plugs into the LC Slot instead of the processor socket where the Apple card is wedged into the system.

The I/O setup is very strange in both cases. I wonder if my Quadra 630 would work with Apple's PC Compatibility Card so long as it had two dedicated monitors even though no edge card connection is provided? Time for a new peripherals thread methinks.