USB Explained

USB technology has been under development since 1993. The first official definition, USB 1.0, was introduced in 1996. It provides a Low-Speed transfer rate of 1.5 Mbits/s for sub-channel keyboards and mice, and a Full-Speed channel at 12 Mbits/s. USB 2.0, which came in 2001, made a leap to Hi-Speed transfer rates of up to 480 Mbits/s. In 2010, USB 3.0 has finally hit the market.

USB 3.0 Specifications

A number of changes have been implemented in USB 3.0 to satisfy the increased demands of external devices. Here is a quick USB technology overview:

• Transfer Rate
• This new Super Speed interface provides realistic transfer rates of around 3,200 Mbits/s or 3.2 Gbits/s. The theoretical top signaling rate is at 4.8 Gbits/s.
• Data Transfer
• USB 3.0 introduces full duplex data transfer. Two of five lanes are reserved for transmitting data, while another pair is dedicated to receiving data, meaning that USB 3.0 can read and write data simultaneously at full speed. Previous USB specifications did not support bi-directional data transfer.
• Power
• The unit load has been increased to 150 mA and a configured device can draw up to six unit loads, which adds up to 900 mA. This exceeds USB 2.0 by 80% and leads to faster recharging or powering of more than four devices from a single hub. In addition, the minimum device operating voltage was dropped from 4.4 V to 4 V, which saves energy.
• Power Management
• USB 3.0 suspends device polling, which is replaced by interrupt-driven protocol. As a result, idle devices won't experience a power drain since a signal from the device is required to initiate data transfer. With USB 2.0 the host controller used to look for active transfers, slowly draining power. Briefly, USB 3.0 supports idle, sleep, and suspend states, as well as link-, device-, and function-level power management ).
• Physical Appearance
• The above described specifications are also represented in the physical appearance of USB 3.0. While the cable was previously described to be thicker because it contains four more wires than USB 2.0, this appears not to be the case now. The plug, however, is a dead giveaway for USB 3.0. It contains an additional set of connectors, as illustrated in the image below.

Firewire 1394

Every device meant to communicate with a PC needs a method of connection. FireWire does have some advantages when compared to other standards.

The brainchild of Apple, the FireWire standard began its existence as a concept in the late 1980′s. The goal of the project was to create a relatively inexpensive, high-speed connection that was easy to use, but Apple did not originally intend for the technology to be used as a connection for external devices. FireWire was used by Apple and by other companies, such as Sony, The standard was presented to the IEEE 1995 as a method of connecting external devices to a computer. It began appearing on Apple and Sony products soon after.

FireWire quickly became popular on audio and video devices like digital camcorders. The reason for this popularity was the speed; the original FireWire 400 standard could achieve a data transfer rate of up to 400 Mbit/s. Which was much faster than USB 1 at the time that could only manage a maximum data transfer rate of 12 Mbit/s. The massive gap in Bandwidth throughput made FireWire an obvious choice for anyone with the need to move large files or caputer data from digital equiped devices like Camcorders.

Speed of data transfer was FireWire's advantage for over a decade until USB 2.0 arrived packing a 480 Mbit/s transfer rate . FireWire responded with the FireWire 800 standard, which boasted a 800 Mbit/s transfer rate. Testing consistently reported that FireWire was better able to sustain a high Bandwidth.

The Uses Of FireWire

FireWire connections are easy to distinguish from USB because they are smaller and tapered on one end, while USB is flat and rectangular. FireWire is most commonly found on audio and video devices like digital camcorders. It's also common to find FireWire on external storage devices like External Hard Drives .The main reason to use FireWire over USB is simply the connection speed. If you have a device that supports both FireWire and USB, you're better off using the FireWire option – unless your device supports USB 3.0.

USB 3.0, which is slowly filtering into the market as it is added to new devices and new PC motherboards, has a theoretical peak transfer rate of 5 Gbit/s. This astonishingly high figure is well in excess of what Firewire can currently manage, which makes FireWire's future uncertain. FireWire has continued to exist solely because it offers a higher data transfer rate than USB. With that advantage gone, the purpose of FireWire remains unclear.

Light Peak, Intel's prototype optical standard that is aiming at sustained transfer speeds of 10 Gbit/s.

eSATA

eSATA is an extension to current serial ATA standards. The main function of eSATA is to make it possible for SATA drives to be attached externally.Relatively new, eSATA means that it is possible to engage in data transfer and processing much more quickly than with traditional methods of connectivity.

How Does eSATA Work?

The basic idea behind eSATA is make it possible to connect multiple drives without having to employ cables or wired connections of some sort. Traditional methods of connecting the external hard drives relied upon the use of such devices as FireWire or USB cables. eSATA does away with all that and makes it possible to connected several external drives in a very short period of time, without all the work of figuring out which cable will do the job. ESATA is based on established standards and will work every time.

What Are Some of the Advantages of eSATA?

One of the immediate advantages of using eSATA is that the eSATA cables are usually longer and easier to distinguish from the jumble of wiring that is used to connect various devices. Anyone who operates even a home system knows how easy it is for wires and cables to become snared as they run across one another and make it virtually impossible to tell what runs where. eSATA cables are generally at least six feet long and tend to be somewhat different in appearance than USB cables and FireWire. One glance at the cable and you know what it is and where it goes.

Another advantage is the ease of connecting and disconnecting the external drive. ESATA drives are designed with what are known as hot plugs. This means the cables can be connected and disconnected with ease, and without the need to power down the system in order to add or remove a drive.

Along with the aesthetics, eSATA also helps to provide excellent rates of data transfer that are sometimes better than can be achieved with a USB connection. There are currently versions of eSATA on the market that will provide data transfer speeds of between 150MBps to 300 MBps. That is a great deal of power when it comes to using an external drive, and is generally much better than can be achieved using a USB cable.