Originally Posted by seablade
What type of drive is this? Personally it sounds like a horrible design. If it can't comfortably be run off Firewire, the limited power from USB will not help much, and if you are going to be that close to overdrawing, it shouldn't exist IMO. Seablade
It does comfortably run solely from a 6-pin FireWire connection or a powered 4-pin FireWire connection like my laptop has. The drive also supports being operated over a USB 2.0 data connection and that does need additional power. I have proven this fact by swapping the 1394 cable with the USB data cable and not plugging in the extra USB power-only cable. The drive clicks and doesn't spin up completely. Attaching the USB power-only cable to the +5 VDC-in port allows the drive to operate. Like I said before, one USB port is NOT enough to power most 2.5" hard drives, hence the second cable. The manufacturer likely wanted to make as universal of a product as possible, and USB users need that extra power even though FireWire users don't. So the +5 VDC port and USB power-only cable are included. I plug in the extra USB power cable when I use the drive (with FireWire) simply because I have the power-only cable, a free USB port, and it cannot hurt.