Firewire allows only one computer connection, the other port is used for cascading two SL AI mixers. But let me ask, why do you need two computers? Capture is integrated in UC Surface (basic functions) and anyway you can toggle between the programs, so they don't need to run on different computers. I do it the way that (I use a Mac mini) UC Surface and Capture do fill only a part of the screen (the programs overlap), so that I can easily "grap" a program. I keep UC Surface at the smallest size, which lets me watch the meters of Capture below. This gives me perfect visual control and everything is "at hand".