4 data and 4 for power as I recall...I did a mod some years back to control an SV Mk1 and a Flextone IIIXL from one FBV. There's 9VDC on the other wires. The reason for doubling up the wire on the power is because it is DC and the longer the cable the more loss there is...There's a post over in the SV forum about it...

http://line6.com/support/thread/1093