Firewire Port Failure Diagnosis?

I moved a number of harddrives around the desk. I realized when I finished that I had completely forgotten to power down the iMac and Firewire drives. When I got them where I wanted them I reconnected the Firewire 800 cable to oneexternal drive and then the Firewire 800 cable to the other drive in a daisy chain, like I've always had. My iMac refuses to ackowledge either Firewire 800 hard drive. The drives have power, I've re-switched the cabling and the ports around, but no success. I'm fairly good at running down broken cables, disconnected cables, etc..

My fear at this point, based on my testing, is that the Firewire 800 Port on the back of my iMac may have failed. I'm running Mountain Lion 10.8.2, and I no longer am aware of how to diagnose an iMac Firewire 800 Port failure. We don't seem to have the Extended Apple Hardware Test in Mountain Lion, like we used to on our earlier Original disks. If that even would been of any use in this case.

How do I proceed???

Thanks 🙂