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USB and IEEE 1394 Guide

USB and IEEE 1394 Guide

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As described in our External Hard Drive buying guide, the USB and IEEE 1394 ports (known as FireWire) are mainstream interfaces for the connection of computer peripherals and devices. What are the advantages of these interfaces and how do we go about recognizing them? Let's find out.

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What is USB?

The USB (Universal Serial Bus) I/O (Input/Output) interface standard is usually featured on computer peripherals and handheld digital devices. The latest revision of this standard is USB 2.0 and the majority of external hard drives utilize one or more USB 2.0 interfaces.

Benefits of USB:

Hot-pluggable: you can plug or unplug an external hard drive while your computer is running. Shutting down or restarting your computer to connect or disconnect your USB peripheral is not required.

Outstanding cross-platform performance: USB can be used on both the Mac and PC. The older USB 1.1 specification operates at 1.5 Mbps in Low-Speed mode and 12 Mbps in Full-Speed mode. With USB 2.0 support, the USB interface provides 480 Mbps bandwidth in Hi-Speed Mode to greatly improve interface performance.

Backwards compatibility: USB 2.0 compliant external hard drives will work on computers that are equipped with only USB 1.1. Although transfer speeds are limited to USB 1.1 spec, however. The USB 1.1 and USB 2.0 ports utilize the same port mechanism.

Provides power to your peripherals: The power provided by the USB bus is sufficient to power certain small form factor external hard drives, e.g. 1-inch and 1.8-inch products. These external hard drive solutions are extremely portable, especially without an AC adapter to carry around.

USB port types on external hard drives

There are three types of USB connectors often found on external hard drives: series "A", series "B" and mini-USB.

Series "A" connector: The series "A" USB connector is often offered in the form of a plug on small form factor (especially 1-inch) external hard drives. All you need to do is simply connect it to a USB port on your computer as computers today typically provide the series "A" receptacle/port as standard.

Series "B" connector: 3.5-inch external hard drives will typically provide one USB series "B" receptacle. You need to use a USB cable (commonly bundled as an accessory) featuring a USB series "A" plug on one end and a series "B" plug on the other to connect the external hard drive to a USB port on your computer.

Mini-USB connector: This connector is very common on 1.8 and 2.5-inch external hard drives. To connect these drives to your computer, please use a USB cable (commonly bundled as an accessory) featuring a USB series "A" plug on one end and a Mini-USB plug on the other end.

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IEEE 1394


What is IEEE 1394?

Like USB, IEEE 1394, too is a high-speed serial I/O (Input/Output) technology that can be found on many peripheral devices. IEEE 1394 goes by a few other names, such as FireWire (Apple), and i.Link (Sony).

There are two IEEE 1394 standards in use today:

1. IEEE 1394a offering 400 Mbps bandwidth;

2. IEEE 1394b offering double the bandwidth of IEEE 1394a currently, and capable of supporting up to 3.2 Gbps in the future;

Both IEEE 1394a and IEEE 1394b are used on external hard drives.

Benefits of IEEE 1394

Cross-platform performance: as mentioned above, both IEEE 1394a and IEEE 1394b offer fast transfer speeds, especially the latter. In addition, IEEE 1394 provides sustained fast data transfer rates, making it extremely suitable for frequent large data transfers often seen in digital video and audio devices and graphics applications. IEEE 1394 is supported by both the Mac and PC.

Hot-pluggable: IEEE 1394 also supports hot-plugging. To use an IEEE 1394-enabled external hard drive, just connect it to a running computer.

Backward compatible: IEEE 1394 is designed to be backward compatible, meaning that an IEEE 1394b-equipped external hard drive can be connected to the IEEE 1394a port of a computer, and vice versa. As IEEE 1394a and IEEE 1394b ports utilize differing port designs, it is necessary to use the right adapter cable.

IEEE 1394 port types on external hard drives

There are three types of IEEE 1394 ports available: 4-pin, 6-pin and 9-pin. The 4-pin and 6-pin ports are compliant with IEEE 1394a, and the 9-pin port supports IEEE 1394b.

4-pin: The 4-pin port is favored by small form factor external hard drives thanks to its thin and small profile. Please note that the 4-pin IEEE 1394 port does not supply power, thus an alternate power source is required. To connect a 4-pin IEEE 1394-equipped external hard drive to the computer, use a 6-to-4-pin IEEE 1394 cable as computers typically often offer 6-pin ports.

6-pin: 6-pin IEEE 1394 ports are frequently used on 2.5" and 3.5" external hard drives. The 6-pin IEEE 1394 port also provides power to the connected device. As a result, an alternate source of power is unnecessary on certain external hard drives equipped with the 6-pin IEEE 1394 port. A 6-to-6 pin cable is needed to connect these external hard drives to the computer.

9-pin: Currently the fastest IEEE 1394 port, it is often used on high-end external hard drives. The 9-pin IEEE 1394b port it is physically smaller than the 6-pin port and isn't used very widely at the moment. In addition, and you may need a 9-to-6-pin IEEE 1394 cable for connection to your computer, which may only provide IEEE 1394a 6-pin ports.

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