I have a couple of these boards but I never did bother figuring it out. Both of my net cities came with them.
There were 2 USB cords in each net city. One went from the NAOMI board to the IO in the CP. The IO had one more USB cord that went back to the VS board and plugged in there (the USB B I think). I would assume you plug the other cabs JVS IO into the free USB A on the VS board.
It has 2 power plugs but only came with one power loom. That was the only thing I never figured out is why there would need to be 2 power sockets on the VS board. When I got the cabs the VS boards were effectively disconnected but one had a power loom laying in the cab.
edit: I looked at the VS board... the part with the power sockets is multi layer i think so you can't see traces. However, the USB sockets are simply straight through to each other. The traces on the board backside are just directly connecting the 2 ports.
I might go mess with my net cities for a minute...
OK, did not power the VS board yet, but I linked the IOs. This had an interesting behavior. The furthest IO from the NAOMI itself was node 1/2, and the one closest to the naomi was 2/2. It appears some games support this and others only listen to IO 1. I tried melty blood actress again and MvC 2 and both knew what to do with both IOs. They set the nearest IO (node 2 technically) to player one, disabled the 2p controls on there, and node 1 (other cab) became p2. I tried Azumanga puzzle bobble, and it only listened to the furthest IO as P1, I could not get p2 to do anything. Most likely just fighting games support it properly.
I didn't have a loom free to power the vs board. The SUN has 3 plugs but 2 are for the NAOMI and one is for the things in the CP that need power (which is the right plug, but I can't pull that to use it). I can grab my spare sun PSU some time and test out the AV splitting.
