I will sum it up for you (c&p from Focusrite_IEEE_1394_compatibility.pdf
However, as there are a wide range of PC manufacturers, a wide range of FireWire hardware is used,
and there are some incompatibilities to be aware of.
Chipset Incompatibilities: The FireWire chip controls all data being streamed to and from the
FireWire port, and certain chips have been known to cause problems with connectivity. We would
recommend using either a Texas Instruments or a VIA FireWire chipset to avoid any such issues.
EDIT: it also says this:
We recommend FireWire 400-only, non-combo (i.e. not with USB AND FireWire ports)
Though it doesn't say anything about FW800's. I would say do some research.
EDIT: EDIT: FW800 info:
LOTS of good enough here too.
http://www.focusrite.com/answerbase/en/ ... php?id=186
Hope that helps. I love my Focusrite LS56 and I am
NO way affiliated with Focusrite, just dig their stuff.