Issue:
This article explains why it may be possible to achieve S800 speed when your 1394b camera is connected to an S400 port on a 1394b PCI host adapter card.

Solution:
In some cases, the 1394a port on a 1394b PCI host adapter card may be improperly configured. As a result, 1394b cameras that are connected to a 1394a port via a 9-pin to 6-pin cable are essentially connected to the 1394b physical layer, making it possible to achieve S800 speeds. However, because the connection has only 6 pins, performance may be unreliable. Point Grey Research does not recommend this configuration for controlling any of our 1394b cameras.

Related Articles:
1.) Differences to consider when selecting an IEEE-1394 PCI / PCMCIA host adapter card.
2.) Some 1394b network configurations cause bus resets and image acquisition problems.
3.) Using PGR IEEE-1394a cameras with 1394b Open Host Controller interface cards.