Apollo Hardware Manual
FireWire Basics
26
Mixing FireWire Speeds
Although FireWire 400 and FireWire 800 devices can be connected to the same FireWire bus via a repeater or
daisy chain, special precautions must be observed to maximize bandwidth in these situations.
FireWire 800 devices on a FireWire 400 bus
FireWire 800 devices are backwards-compatible and can be connected to a FireWire 400 bus using a 9-pin to
6-pin FireWire cable or adapter. However in this scenario any 800 megabit-capable devices on the bus
(including Apollo) will operate at a maximum of 400 megabits because FireWire bandwidth cannot exceed the
maximum bus speed of the host computer.
FireWire 400 devices on a FireWire 800 bus
FireWire 400 devices can be connected to a FireWire 800 bus using a 6-pin to 9-pin FireWire cable or adapter.
However, if the FireWire 800 devices are located after the FireWire 400 devices in the daisy chain, all FireWire
devices will operate at a maximum of 400 megabits because the FireWire 400 devices force all subsequent
devices to run at FireWire 400 speeds.
It is possible to configure a FireWire bus to run at both FireWire 400 and FireWire 800 speeds simultaneously if
the host computer bus is FireWire 800, supporting maximum throughput with a mix of FireWire 400+FireWire
800 devices. This is accomplished by putting any/all FireWire 400 devices AFTER any/all FireWire 800 devices in
a daisy chain or tree chain. If (and only if) FireWire 400 devices are attached to a FireWire 800 bus after the
end of all FireWire 800 devices in a daisy chain or tree chain, the FireWire 800 devices will operate at 800
megabits while the FireWire 400 device operates at 400 megabits. The diagram below illustrates the
recommended configuration when Apollo is sharing a FireWire 800 bus with FireWire 400 devices.
Recommended Mixed Speed Setup
The example below shows the correct method of interconnecting FireWire 800 and FireWire 400 devices to a
FireWire 800 computer bus. Any mixture daisy chains, repeaters, and/or tree chains may be used, as long as all
the FireWire 400 devices are placed after all the FireWire 800 devices.
This FireWire bus runs optimally at both 800 megabits and 400 megabits because
the FireWire 400 device is located AFTER the FireWire 800 devices in the setup.
