It's same for Firewire800 (1394B) and FireWire400 (1394A).
2.5" drive: no external power needed.
3.5" drive(s): external power required.
Laptop slim optical drive: no external power needed.
Desktop optical drive: external power required.

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Added on January 22, 2008, 9:35 amFireWire400 comes in different flavor. 4pin for portable device or standard 6pin. Sony just gave it a different name so it sounds "exclusive" to them.
http://en.wikipedia.org/wiki/FireWire

And FireWire800 are backward compatible with FireWire400. Let's say I have FireWire800 external drive. But my older Mac only have FireWire400, I can easily get a plug converter or cable to hock them up.

This post has been edited by wei: Jan 22 2008, 09:36 AM