The New Firewire 800 Standard
The faster 800Mbps Firewire
standard is called Firewire 1394b, FireWire 800 or just FireWire B.
FireWire 800 standard cables offer a much higher total data speed, 800Mpbs, twice that of the original FireWire standard. They use a special 9-pin
connector, compliant with the IEEE 1394b standard, and in addition to speed increases have some new features that improve reliability of data. You will use these cables with new, faster 800Mbps products.
How Firewire 800/Firewire1394b works
If you plug a FireWire 800 device, like a hard drive, into
a FireWire 400 (or 1394a) port it will still work. But it will not give you 800 performance unless you use 800Mbps cables and connect to an 800Mbps FireWire port. Furthermore, 800 devices have 9 pin Firewire ports where
400 devices have 6-pin ports (and there are connectors with their own 4-pin connections). So depending on your computer and your FireWire device, there are a few possibilities.
Firewire beta and bilingual cables
"
Beta Firewire cables" refers to the true FireWire 800 cable, intended for connecting a 1394b device with a 1394b port on your personal computer. Both ends will have
a 9-pin connector, compliant with the 800 standard, and are designed to get all the speed of FireWire 800.
"Bilingual Firewire cables
" refer to those that have a 9-pin connector on one end, for a 800Mpbs device or port, and an "A" connector, either 6-pin or 4-pin, on the other. FireWire 800 is backwards
compatible so if you have a FireWire 800 device but your computer is still FireWire 400, you can still plug and play, although you'll need one of these special cables and you'll miss out on some of the speed of FireWire
800.
There are two types of bilingual cables available for mixing 800 and 400 devices:
9-pin to 6-pin - For connecting a standard FireWire device or computer to an 800Mbps connector.
9-pin to 4-pin - For connecting an 800Mbps device or computer port to a 4-pin connector
Firewire Cable Length
The maximum cable length for connecting device to device with a 400Mbps cable is 4.5m (14.85ft).
The Firewire specification calls for 10 meter (32ft) cables that may be used
in conjunction with a repeater when it is necessary to extend FireWire cables. Because this cables are not reliable in some situations we strongly suggest you to use 4.5m cables and hubs when needing to extend to
greater distances. 
Signals on the 9-pin FireWire 800 Connector
Pin |
Signal name |
Description |
1 |
TPB– |
Twisted-pair B Minus |
2 |
TPB+ |
Twisted-pair B Plus |
3 |
TPA– |
Twisted-pair A Minus |
4 |
TPA+ |
Twisted-pair A Plus |
5 |
TPA (R) |
Twisted-pair A Ground Reference |
6 |
VG |
Power Ground |
7 |
SC |
Status Contact (no connection; reserved) |
8 |
VP |
Power Voltage (approximately 12.8 V DC) |
9 |
TPB (R) |
Twisted-pair B Ground Reference |
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