Idézet: Desorder - Dátum: 2005. okt. 26., szerda - 22:47
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USB 2.0 - Hi-Speed USB - FAQ
What is USB 2.0? Add Your Notes
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.' Though some manufacturers label their products Full-Speed USB. Note that this seems a bit deceptive. It�s easy to mistake Full-Speed for Hi-Speed.
You won't be fooled from now on as you now 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. You as a consumer don't need to figure out all the jargons. Just keep in mind that only 'Hi-Speed USB' and 'USB' host and devices exist.
How do I know if my PC has USB 2.0? Add Your Notes
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).
These drivers are provided by the manufacturer, and may carry the maker?s name (i.e. ADS, Belkin, IOGear, Siig, etc.). There should also be two ?standard? version USB host controllers present as well. They are embedded in the USB chip which routes the differing USB speeds accordingly without user intervention.
There are currently 6 manufacturers of the Hi-Speed USB host silicon themselves:
* ALi (Acer Labs)
* Intel
* NEC
* SiS
* VIA
* nVidia (shows as "Standard" controller
Any other brand name that appears in Device Manager would likely be an add-in Hi-Speed USB PCI card. The makers above do not make add-in cards, but they do make the chips that are used in them.
How do troubleshoot "unknown device" error listed in Device Manager? Add Your Notes
I wish that there was a simple, single answer for this. There's only one thing more distressing - no device recognition at all. Here are the most likely culprits:
* The USB device or the USB adapter requires it's own power source. If your USB device or adapter came with an AC power "brick", try connecting it.
* Here's a likely one - the front USB ports on your PC case may be misconnected. I've seen them that way from the factory. It's a good idea to check the connections against specifications. The standard order of connection is Red, White, Green, 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. I've seen many new USB devices that do not work. 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.
I will now discuss 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 manufacturer's web site.
2. Try uninstalling the unknown device, unplugging the device and rebooting. Replug when back in Windows.
3. Be certain that you have the correct drivers! You may have gotten the wrong CD or a CD with drivers for more than one device on it.
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 replug USB devices one at a time.
Just remember that you are entitled to support from the device maker. If you can't get help, do not hesitate to return the device. Some manufacturers only seem to respond to lost business. It's a shame, but it's true. Send them a message - that you won't accept shoddy goods or lackluster support.
By William DeVercelly
How fast is USB 2.0? Add Your Notes
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.
How will consumers benefit from USB 2.0? Add Your Notes
With speed 40 times more than that of USB 1.1, USB 2.0 broaden the range of external peripherals that can be used on a computer. Even with multiple high-speed peripherals connected to a USB 2.0 bus, the system will less likely to hit the bandwidth bottleneck. The new specification also inherits the current USB�s Plug and Play and hot-swapping capability as well as providing backward compatibility for USB 1.1 hardware, allowing existing user base to upgrade seamlessly.
Do USB 2.0 & USB 1.1 hardware work interchangeably? Add Your Notes
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.
When it comes to USB hub compatibility between USB 2.0 and USB 1.1, here some facts:
* A powered hub is always preferable to unpowered.
* USB hub ports are not as capable or flexible as real PC 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 drives are 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.
By William DeVercelly
Will USB 2.0 replace USB 1.1? Add Your Notes
Not entirely, because many products such as generic keyboards, mice, joysticks and audio speakers do not require the faster speed of the new USB 2.0 technology. Only bandwidth-hungry devices, such as webcams and high-capacity storage systems, will need all the speed. However, next-generation systems will come with USB 2 ports rather than USB 1.1.
How do I distinguish between a USB 2.0 and a USB 1.1 device? Add Your Notes
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. However, most people won�t miss it as manufacturers often label �USB 2.0 READY� or �40 times faster than USB 1.1� on the boxes.
Will USB 1.1 devices run any faster on a USB 2.0 bus? Add Your Notes
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.
What are USB Hi-Speed and USB Basic Speed logos? Add Your Notes
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.�
Under a license from USB-IF, products must pass the compliance tests before manufacturers can use one of the two trademarked logos. The Promoter Group will take legal actions on manufacturers that label either logo on their products, which have not passed the tests.
What happen if a USB 2.0 device is plugged into a USB 1.1 system? Add Your Notes
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.
What is the max. length of a USB 2.0 cable? Add Your Notes
5m. However, if you cascade 5 hubs with 5m USB cables, this will allow you to connect a device 30m away.
What do I need to use a USB 2.0 device? Add Your Notes
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.
How much will it cost to upgrade to USB 2.0? Add Your Notes
Around $80 to $150. Currently, Orange Micro., Adaptec and IO Gear are shipping USB 2.0 PCI cards, some of which even have FireWire ports. Interestingly, almost all USB 2.0 PCI cards include an internal port, which is probably for connecting internal USB 2.0 IDE enclosure or USB 2.0 front panel.
Will USB 2.0 arrive on mobile computers? Add Your Notes
Yes, but not in integrated solution on laptops. You will need a USB 2.0 CardBus card. Orange Micro. is shipping USB 2.0 compliant 4-port CardBus card. Eventually, notebook vendors will adapt to USB 2.0 technology, and we will see USB 2.0 ports on laptops. This transition won't happen until 2002 at the earliest.
Which operating systems support USB 2.0? Add Your Notes
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.)
The software company is still considering USB 2.0 support for Windows ME, but it already has decided not to bring USB 2.0 to Windows 98 and Windows 98 SE. If you have Windows 98, you will have to rely on 3rd party USB 2.0 support from USB card manufacturer.
As for Mac users, Orange Micro. and KeySpan are providing USB 2.0 for MacOS X exclusively.
Do USB 1.1 cables work with USB 2.0 devices? Add Your Notes
Ideally, yes. USB 2.0 architecture uses the same cables and connectors as USB 1.1 compliant products. Unforunately, 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, most vendors include USB 2.0 compliant cables with their USB 2 PCI cards and peripherals.