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You're at: Home > Support & Download > FAQ > Understanding USB
 
Understanding USB


 
  1. Do USB 2.0 & USB 1.1 hardware work interchangeably?

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 maintain 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 SYBA's USB 2.0 Host Controllers will work with 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.

When it comes to USB hub compatibility between USB 2.0 and USB 1.1, here are some facts:

  • A powered hub is always preferable to un-powered. Our USB2.0 Hubs are self powered.
  • USB hub ports are not as capable or flexible as real C ports so it;s best not to expect the world of them.
  • USB 1.1 (obsolete) hubs will work fine on USB 2.0 ports, but they cannot utilize USB 2.0 capabilities. They will default to slower speeds.
  • Hi-Speed and Full/Low-Speed USB devices can coexist nicely on USB 2.0 hubs. Connecting such a hub to a USB 2.0 port is recommended.
  • USB 2.0 hubs can be used on older USB 1.1 computers.
  • Although it is said that you can "cascade" up to 4 hubs, problems may start to arise after two hubs, it's best to minimize hub usage if possible.
  • Many USB devices don't work well on hubs. Cameras, scanners and especially USB drivers ae known to have problems with hub connectivity.
  • Remember that "active USB extensions" are really just one-port hubs.

As you can see, there are very few issues (if any) to be concerned about when mixing USB types. If the system and devices are healthy, it should be a "no-brainer" to connect any USB device - provided that you follow manufacturer’s instructions.

  1. How do I know if my PC has USB 2.0?

You can identify whether your PC has Hi-Speed or not relatively easy. Open Device Manager and expand the Universal Serial Bus section. There should be an "Enhanced" USB host controller present.

Windows 98 systems may use a different name, because Hi-Speed USB drivers in these operating systems are not provided directly from Microsoft (Windows ME, 2000 and XP get their drivers through Windows Update).

  1. How to troubleshoot "unknown device" error listed in Device Manager?

Here are some reasons why such error occurs:

  • The USB device or the USB adapter requires its own power source. If your USB device or adapter came with an AC power adaptor, try connecting it.
  • The front USB ports on your PC case may be misconnected. It's a good idea to check the connections against specifications. The standard order of connection is Red, White, Green, and Black. No more than 4 wires per USB bank are needed.
  • Defective device. Do not assume that all PC components work correctly out of the box. If you can, try the device on another PC.
  • All drivers are not installed. Some devices will require installing the driver package before plugging in the device. Some devices will also require basic USB files from the Windows CD before the unit will function. The general rule is to always follow installation directions precisely and to have the Windows CD ready.

How to address an "unknown device" problem which is caused by a driver deficiency?

  1. Try to update the unknown device driver from within Device Manager. First try letting Windows search for one. If that fails, go back and choose "Select from a list" and then "Have disk". Browse to the device CD and look for the appropriate Windows folder there. Try browsing to the Windows CD (Win9x folder or i386 folder). Lastly, try updated drivers from the SYBA's web site.
  2. Try uninstalling the unknown device, unplugging the device and rebooting. Re-plug when back in Windows.
  3. Be certain that you have the correct drivers.  
  4. Cleaning up in Safe Mode may be necessary. Unplug all USB devices. Reboot the PC. To enter Safe Mode, press the F8 key repeatedly while restarting the PC. Timing is important. Try to press quickly before the Windows logo screen appears. Pressing and holding the CTRL key may work too. Choose Safe Mode and open Device Manager. In Windows 2000 and XP, click View > Show hidden devices. Now locate all USB devices, HID (Human Interface Devices), USB drives and controllers/hubs. Remove all and save the USB Host Controllers for last. When done, restart and re-plug USB devices one at a time.

 

  1. How fast is USB 2.0?

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.

  1. Which operating systems support USB 2.0?

Microsoft has released the official USB 2.0 driver for Windows XP and Windows 2000. The version is 5.1.2600. The software is available on-line at Windows Update website. (If you don't have a USB 2.0 card installed in your system, Windows Update won't list the USB 2.0 driver as an update.)

  1. Do USB 1.1 cables work with USB 2.0 devices

Ideally, yes. USB 2.0 architecture uses the same cables and connectors as USB 1.1 compliant products. Unfortunately, only 3 out of 11 cables on the market are certified as USB 1.1 compliant. You may run into the cables that cause problems connecting high-speed peripherals. To avoid negative user experience, SYBA have included USB 2.0 compliant cables on select USB 2 PCI cards and other connectivity products.

  1. What is the maximum length of a USB 2.0 cable?

5M., however, if you cascade 5 hubs with 5M USB cables, this will allow you to connect a device 30M away.

  1. What are USB Hi-Speed and USB Basic Speed logos?

These logos are part of USB Promoter Group’s branding program that ensures the quality of USB products. The USB 2.0 certified products would display a blue, white and red logo, bearing the words “Certified and Hi-Speed”. The classic USB 1.1 certified products would display a black and white logo with the words “USB” and “Certified.”



All SYBA USB connectivity products have passed rigorous tests to allow the display of all USB certified logos on our packaging.

  1. What is USB 2.0?

Finalized in 2001, USB 2.0 is a complete overhaul to the Universal Serial Bus input/output bus protocol which allows much higher speeds than the older USB 1.1 standard did.

USB 1.1 allowed a maximum transfer rate of 12Mbits/second. That rate is now called 'USB.'

Be aware that Full Speed USB is only 12Mbits/second where Hi-Speed USB mode is capable of a much faster 480Mbits/second.

As an aside, USB mice and keyboards need only 1.5Mbits/s to function. That performance level is also named 'USB' by the USB Promoter Group.

To sum it up, USB 2.0 specification incorporates three speeds: Hi-Speed, Full-Speed and Low-Speed.

What happens if a USB 2.0 device is plugged into a USB 1.1 system?

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.

  1. What do I need to use a USB 2.0 device?

The requirement is similar to that of USB 1.1, but all components will have to be USB 2.0 compliant. A successful USB 2.0 connection requires a USB 2.0 host controller card, a USB 2.0 driver and a USB 2.0 peripheral.

  1. Will USB 1.1 devices run any faster on a USB 2.0 bus?

No. However, the new USB 2.0 architecture allows more high-speed USB 1.1 devices, such as web cams, audio devices, to share the bandwidth. SYBA follows 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.

  1. How do I distinguish between a USB 2.0 and a USB 1.1 device?

New logos designed by the USB Promoter Group allow consumers to easily identify the new USB 2.0 products. The new colorful logo for USB 2.0 is labeled USB Hi-Speed, and the new logo for USB 1.1 is labeled with USB Basic Speed.

 

 

 

 

 


 
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