USB 1.1 & 2.0 mixed devices

[jgeidl]

It is my understanding that mixing 1.1 and 2.0 USB devices on the same hub will cause all of the devices to drop back to 1.1 speed.

I am wondering if I have one hub dedicated to 1.1 devices and one hub dedicated to 2.0 devices will they all drop back to 1.1 since they are ultimately plugged into the same computer?

Jim

 

[bcastner]

If the hub is 2.0 compliant, there should not be an issue mixing the two USB types.

 

[jgeidl]

Not according to D-link and Linksys. According to them, mixed devices will force all to drop back in speed to the slowest device. Truthfully, I had not ever heard this before today.

As long as we are on the subject, got any ideas on how to tell what speed a USB is operating at?

Jim

 

[garebo]

I would like to know how to do that as well, that is, find out speed a usb device or even a firewire device is actually running.
I remember asking quite some time ago and got no response, figured i guess there isnt a prog out there to do that, which seemed odd at the time. Maybe it was my deodorant, lol.


Good advice + great people = tek-tips

 

[bcastner]

I just Googled this and there are a hundred sources saying that Linksys and D-link are flat out wrong.

From the USB Consortium - the Industry Group for the USB standard:

Mixing Different-Speed Devices on a Single Port
If you are using one USB device or a single USB device per computer port, there are no issues concerning mixing devices of different speeds. If you have a USB 2.0 port, you simply plug in any USB device. The system will recognize the device’s speed and communicate accordingly.

If you plug a high-speed 2.0 device into a 1.1 port, the device should be recognized, installed, and actually work. However, you will not necessarily achieve the sample rates that you would obtain from a 2.0 port.

To connect more than one USB device to a single port on your computer, you must install a USB hub. Hubs are available in both 1.1 and 2.0 configurations. You may plug any combination of 1.1 and 2.0 devices into either hub, and they should work.

You also may mix low-speed, full-speed, and high-speed devices on a single hub without typically reducing the performance of the higher speed devices. To take advantage of high-speed transfers, the device, the hub, and the computer port all must be 2.0. The USB has been designed to minimize, if not eliminate, the penalty for mixing older and newer technology.

 

[bcastner]

A good resource for answers to USB questions is the web site "Everything USB." For example, the mixed devices question is answered several times, including in the FAQ on the site:

http://www.everythingusb.com/forums/showthread.php?s=72df522255adeb674a14989e55eb381b&threadid=798

Your speed questions can also find their answers there.

 

[bcastner]

Just as a last point, a USB 2.0 controller device has three controller chips - one for USB 2 devices, one for USB 1.1 devices, and one for USB 1.0 devices. This design is to prevent the mixed device slowdown claimed in the posts above: "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."