USB 2.0

USB 2.0 is the next version of the USB protocol aimed at expanding the capability and bandwidth or USB to meet the needed of more demanding peripherals, like video-conferencing equipment and external hard drives. The theoretical speed capacity of USB 2.0 is 480 Mbps, all while being backward compatible with all existing USB hardware and wiring. In fact, current USB wiring will run and support USB 2.0, so no wiring changes are needed.

USB 2.0 will change the protocol by using 1/8 millisecond frames rather than the 1 ms frames of the 1.1 specification. USB hubs for 2.0 will play a big part in the backward compatibility. The hub will determine on a device-by-device basis whether the device can handle the USB 2 spec. If it cannot, it will operate as a USB 1.1 spec at 12 Mbps.  Seeing that the hub may very well be accepting transactions at the full 2.0 spec while trying to output them at the 1.1 spec, the hub has to become a bit more complex bith in circuitry as well as the addition of buffers. The host software will play a role in detecting unoptimimum configurations and notify the user. This is because USB 2.0 hubs need to be placed in certain configurations in relation to the USB 1.1 hubs so that everything operates at the speed it was designed to.

Firewire

Firewire is another high-speed interface for connecting external components. Originally developed by Apple Corporation, the interface was a bit slow to catch on mainly because people thought it was TOO fast, and too expensive to implement in comparison to USB. It didn’t really gain any horsepower until Sony included a Firewire port on one of the digital video cameras. in 1995. Later in 1995, IEEE (Institute of Electrical and Electronics Engineers, Inc.) accepted it as a standard, which is why it is now somtimes dubbed IEEE 1394.

With a 400 Mbps bandwidth capability (1.2 Gbps in the works), Firewire is able to be used to attach external storage devices, burners as well as digital multimedia devices to your PC. One can daisy-chain up to 63 Firewire devices onto one single PC without the use of hubs. Like USB, it is fully plug-and-play and hot-swappable. The firewire protocol works similarly to USB. Each device is assigned an address in an enumeration process. The host manages which driver to use or if a new driver is needed. The actual data transfer protocol does differ, though.

The information packet in IEEE 1394 is based on the IEEE 1212 spec. Each packet is 64-bit: 10-bit Bus ID to identify where the data is from, 6-bit physical ID to ID which device sent the data, and a 48-bit storage area. The wiring itself has two twisted pairs for data transfer, and two for power.

The major difference between Firewire and USB is similar to the differences bertween SCSI and IDE for hard drives.

• While USB expands through hubs, Firewire is daisy-chained (like SCSI)


• While USB need connections to the computer in order to communicate, Firewire is peer-to-peer, meaning devices can “talk” to each other without going through the PC.

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