When you say "connect", I would guess you are talking via midi ? Or do you want to do audio from both into SB instead ? I have SB Live, which I use primarily for working with soundfonts. I have had more then one board connected to it via midi. In fact right now both my PA80 and Motif are connected. SB Live has the joystick port for midi in and out. I have the corresponding cable for the SB which has a joystick plug on one end and 2 standard 5 pin midi connectors on the other. My setup is as follows:

SB Live out to Motif in. Motif out to SB live in. Motif midi thru to PA80 in. In this way what plays via midi coming out of the SB can be heard on both boards. I can only send midi data back into the comp using the Motif as I have it set up now. I could also send data back into the comp from the PA80 ( PA80 midi out is inactive the way I have it setup now ) if I was to use a PC to host cable from the comp to the PA80 and install Korg drivers onto the comp, but I only need to play the keys on one board, and I like the key feel better on the Motif, so I never bothered.

Hope this helps a little.

AJ