Missing Hard Drives PERC 6/i

I just picked up a new PERC 6/i controller for my Poweredge 1800. I am using 2 SAS to SATA cables (the ones that break the connections out to 4 SATA harddrives) It will only recognize the drives attatched to one of the cables. I am trying to connect 6 hard drives and can only get 4. Is there something I need to do to get more than 4 hard drives to be recognized? I tested the cables and they appear to be good.