For a client I am cutting together a 6-camera XDCAM HD shoot. Doing it on an i7 iMac.
I have each camera's vision on a separate external Firewire800 drive.
Have made the multiclip successfully using all cameras and got it onto the timeline.
Now, because there are 6 cameras, I need to use the 9-up view in the viewer. However, when I do select 9-up, a red bar appears above the timeline and of course, needing render, I can no longer play the timeline for editing the multi cams together.
When I switch back to 4-up, the red bar goes and I can play the timeline as I should be able to...
Xdcam is a very processor intensive codec. And you have 9 streams of this codec.
Your setup isn't capable of this. For this many streams I'd HD you need a really fast RAID, far faster than a FW800 mirrored raid. Even at RAID 0 it would be too much for the drives and computer. Your setup is fine for a lot of basic editing workflows, but (oh, 6 streams of video. Still too much) this many streams of HD requires a better setup.