I've connected a 2 TB ext. HDD to my MacPro 8core. The MacPro has 2 boot partitions - - 10.6.8 and 10.8.2. When I boot in 10.6.8 (with the ext. drive either FW400 or USB) the Mac sees the ext. drive as soon as the desktop comes up. And when I boot in 10.8.2 with the ext. drive USB-ed, again, instant recognition. *BUT* when I boot in 10.8.2 with the external connected to the FW400 - - the combo I would prefer - - it takes the Mac from 80-90 seconds from desktop to seeing the drive.