Firewire 800 doesn't work with 800 female to 400 adpater, won't power up the drive, I guess it need power over the extra pins. (I wonder whether 9-pin to 6-pin would work with powered 6-pin 400 port). Won't power up plugging in a Lacie d2 Bigger Extreme 1TB Fire 800 drive 2nd port either. Doesn't work with SIIG 2-port Firewire 800 ExpressCard/34 NN-000042-S1, but it works if you use optional 12V power supply to supply more juice). It also work when controller straight off system board.
Seagate GoFlex 500GB and 500GB Pro (7200rpm)
HP HPX, Vista 64-bit
Seagate GoFlex 500GB Pro (7200rpm)
T410, Windows 7 32-bit
Note: the write number is way off, always have problem with write with Firewire 800 with ExpressCard and Windows 7 for some reason.