holy jeebus, i had never heard of this board. but a quick search found this bit of oddity:
"DVI-to-DVI Connection
Connect one end of the DVI cable to the DVI connector on the SDI Output card and the other end to the "north" DVI connector on the NVIDIA Quadro FX 4600/5600 card as shown. The SDI output will not work if the cable is not connected to these two connectors."
So it was an external pass thru type system that just converted DVI to SDI. They joined the daughter card via external oddball cable rather than making an internal ribbon cable connection.
Yep, it was just to convert computer graphics into broadcast TV world. Probably powering a bunch of TV stations weather broadcasts for the next decade.
That's still a few rungs up from the older skool tech of a large round table top with the different gauges for things like temp/pressure/humidity/etc on it that rotated at a set speed with a stationary camera mount so that the gauges would spin underneath it. For a lot of small cable companies this was the "weather" for that cable company. It would be setup at the head end where all of the various satellite dishes were pulling the feeds. An ex-coworker's family was responsible for that existing, so I used to hear all sorts of "back in the day" themed stories about it.
