You may have heard that USB 2.0 is "backward-compatible" with USB 1.0/1.1 (Full-Speed USB). While that's true, USB 1.1 is also forward-compatible with USB 2.0. Whenever a system has USB 2.0 ports, you'll find the "Enhanced" USB controller in Device Manager, but you will also find two other USB controllers. These two to mantain backward compatibility to USB 1.1 devices. Each USB 2.0 host actually has 3 chips onboard. The USB controller routes signals to the correct controller chip depending on how a device is recognized. Where a device is physically plugged in has no bearing on how it is routed. All ports on a USB 2.0 motherboard can host any USB devices at all as long as the system and devices are healthy.

The vast majority of USB 2.0 devices will work on older PCs and Macs. None should flat-out fail unless there are other issues with the system. Hi-Speed USB devices will revert to Full-Speed operation when connected this way. Understand that Hi-Speed is at least ten times faster than Full-Speed in actual operation, so the speed difference is quite noticeable? unless you have never experienced Hi-Speed, of course.

The entire bus under the USB 1.1 root hub will slow to 12Mbps. The operating system will probably notify the user about the sub-optimal configuration and recommend for a better course of action.

If several USB 1.1 hubs are connected to a USB 2.0 bus, then each of the USB 1.1 hub will get a full 12Mbps bandwidth.

USB 1.0 can operate at 1.5 Megabits per second (Mbps).

USB 1.1 allowed a maximum transfer rate of 12Mbits/second. USB mice and keyboards need only 1.5Mbits/s to function. That performance level is also named 'USB'.

USB 2.0 has a raw data rate at 480Mbps, and it is rated 40 times faster than its predecessor interface, USB 1.1, which tops at 12Mbps. Originally, USB 2.0 was intended to go only as fast as 240Mbps, but then, USB 2.0 Promoter Group increased the speed to 480Mbps in October 1999.

You can use USB device with USB 1.0, USB 1.1 and USB 2.0 as long as your PC or laptop has USB ports, but USB 2.0 device transfer data at 480 Mbps on systems with USB 2.0 support only.

Universal Serial Bus, or USB

This competing serial input/output technology was introduced in 1997. USB ports are found on most desktop PCs, notebooks, and peripherals today. There are far more USB devices than there are FireWire peripherals. The new USB 2.0 specification promises data transfer rates of 480 mbps, which is 80 mbps faster than FireWire. USB 2.0 devices are backwards-compatible with USB 1.1 ports. While you won't get the increased speeds, you can use a USB 2.0 device with your current notebook's USB 1.1 port.

No. However, the new USB 2.0 archiclecture allows more high-speed USB 1.1 devices, such as webcams, audio devices, to share the bandwidth. Developers need to follow USB 2.0 spec in order to design higher speed peripherals that can take advantage of the extra bandwidth. USB 1.1 devices still operate at 12Mbps at full-speed and 1.5Mbps at low-speed on a USB 2.0 bus. Even though USB 1.1 devices won't run any faster, they can work alongside of USB 2.0 devices on the same bus.