Universal Serial Bus (USB)

USB (Universal Serial Bus) is a new external bus developed by Intel, Compaq, DEC, IBM, Microsoft, NEC and Northern Telcom and released to the public in 1996 with the Intel 430HX Triton II Mother Board. USB has the capability of transferring 12 Mbps, supporting up to 127 devices and only utilizing one IRQ. For PC computers to take advantage of USB, the user must be running Windows 95 OSR2, Windows 98 or Windows 2000. Linux users also have the capability of running USB with the proper support drivers installed.

There are several different editions of the USB standard that have been released:

USB 1.0, the first edition, was released in January 1996. It supported 1.5 Mb/s (low speed) and 12 Mb/s (high speed) transfer rates. Note that this is Megabits per second and not MegaBytes per second -- a common misunderstanding. A percentage of this data rate is reserved for USB protocol overhead, so the actual data transfer is less than the indicated speed. How much less depends on the transfer type and the packet sizes.

USB 1.1 was released in September 1998. This edition fixed many of the problems in release 1.0.

USB 2.0 was released in early 2000 and has increased the maximum transfer speed by a factor of 14 up to 480 Mb/s! USB 2.0 is backwards compatible with USB 1.x. Although the USB 2.0 specification has been released, operating programs for personal computers are not expected to have USB 2.0 support until about the fourth quarter of 2001. A few peripherals supporting USB 2.0 have already begun to show up on the market in late 2000.

USB memory drives

USB Memory is a small USB device that is used to store data. It allows users to easily move data from one computer to another. These devices are not recommended as a backup device. USB Memory can be purchased as large as 4GB. We recommend 1GB or more. USB Memory is made by many different manufacturers and can be found in many different forms. Some more common device names include USB memory keys, pens, and sticks. Make sure to get USB 2.0 memory to get the fastest data transfer rate available. Windows Vista can use USB memory to boost it's RAM.

USB memory drives can be treated similarly to a removable disk drive, and imaged and analyzed using conventional forensic
tools. Many manufacturers produce USB memory drives of various capacities. Currently, however, very few PDA devices support host USB ports, which are needed to interface with these peripherals. Moreover, few if any USB drive manufacturers provide the necessary drivers for PDA operating systems. This situation is understandable given that host USB specifications intend for an interface to be capable of supporting multiple devices sharing the port, which if permitted would place a significant power drain on the battery of the device. Other factors include the restrictions in mobility imposed by a USB drive sticking out of the side of a PDA compared to the benefits of providing one or more memory card slots that completely contain a card when inserted.

As with memory card extensions, USB drives may offer additional capabilities such as a wireless interface. Access to memory contents may also be protected through a built-in fingerprint reader or some other mechanism such as a smart card, which complicates the
acquisition process. However, for the reasons mentioned above these peripherals are not normally associated with PDA devices.

USB 3.0 drive

USB 3.0 (aka SuperSpeed USB) is a major update to USB 2.0 that promises higher performance with better power management. It was first introduced on September 17, 2007 at the Intel Developer Forum.Transfer rates can go up to 4.8 Gbits/s as opposed to USB 2.0’s 480 Mbits/s. This means USB 3.0 can be up to 10 times faster than its predecessor! It is achieved through the SuperSpeed technology which allows multiple streams of data transfer. However, the fastest USB 2.0 drives are only able to reach about 50% of their theoretical bandwidth cap, topping out at around 250Mbits/s. The first USB 3.0 devices to reach the market will probably run at only 1.4Gbits/s, far beneath the 4.8Gbits envelope yet substantially faster than any USB 2.0 device. Second generation USB 3.0 devices can be  expected to rival SATA‐II performance with actual transfer speeds eclipsing 2Gbits/s. 

Video is one of the big drivers for higher speed. Handheld video cameras are pervasive. HD video uses massive amounts of storage, and transferring video through USB 2.0 takes a lot of patience. This isn’t just for video professionals, but average consumers with digital video cameras.  

External removable storage also is in desperate need of a speed boost, both for transporting and backing up data. eSATA is fast, but doesn’t have broad enough adoption in the market. USB 3.0 will replace eSATA and FireWire as the de facto high speed external interface. 

USB 2.0 has 4 wires: two data lines, power and ground. USB 3.0 uses an additional 5 wires – two transmit lines, two receive lines and an additional ground – for a total 9. The extra wires constitute an additional bus that works in parallel with the HighSpeed USB 2.0 port.   USB 3.0 cables have two additional shielded differential pairs (SDP) of wires for a total of 9 
signal wires. 3.0 cables have to be shielded to prevent electromagnetic interference and maximize signal integrity. This means the cables are thicker, heavier, less flexible and more expensive than 2.0 cables.