In short, the 6 wire can carry power to the device.
In a nutshell, a 4 wire device can be wired to a 6 wire port but not always the opposite.
Bob
I'm looking at purchasing an external hard drive that connects via firewire(IEEE 1394). It seems there are two kinds, 4 and 6 wire. I have a PCI firewire card that I know accepts the 4 wire variety . What is the 6 wire used for? and will my card accept both?

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