add arrow-down arrow-left arrow-right arrow-up authorcheckmark clipboard combo comment delete discord dots drag-handle dropdown-arrow errorfacebook history inbox instagram issuelink lock markup-bbcode markup-html markup-pcpp markup-cyclingbuilder markup-plain-text markup-reddit menu pin radio-button save search settings share star-empty star-full star-half switch successtag twitch twitter user warningwattage weight youtube

Question regarding backwards compatibility for USB

Root_User

7 days ago

When using a USB 1.1 device in a USB 2.0-capable port, would all other devices connected to the same root hub be limited to USB 1.1 speeds, or are they independent in this respect?

What about USB 2.0 devices in USB 3.0 ports, or USB 2.0/3.0 devices in USB 3.1 ports?

Please mention sources in your responses, if possible. There seem to be quite a few conflicting claims out there.

Comments

  • 7 days ago
  • 1 point

When using a USB 1.1 device in a USB 2.0-capable port, would all other devices connected to the same root hub be limited to USB 1.1 speeds, or are they independent in this respect?

Provided the hub is properly wired with a full allocation of bandwidth and power they are independent.

When You activate a connection on USB it allocates its total bandwidth to that connection no matter which standard is connected to it.

So a 1.1 will be limited to 1.1 speeds because it is a 1.1 connection and can't use more then that, 2.0 will be 2.0, 3.0 will be limited to 2.0 and so on.

Things like power draw off of the port can get sketchy, but the data rate is fixed by the ports.

Now there are instances where that is wrong because the hub isn't properly supported with bandwidth, so plugging in two 3.1 for example causes bandwidth sharing, but that is an implementation fault not the hubs fault.

Most of the confusion comes from manufacturers not fully supporting the standards or using bandwidth sharing.

  • 7 days ago
  • 1 point

When using a USB 1.1 device in a USB 2.0-capable port, would all other devices connected to the same root hub be limited to USB 1.1 speeds, or are they independent in this respect?

They are independent.

So a USB 1.1 device will work at that speed regardless if you connect it to a USB 2.0 or USB 3.0 port.

Also a USB device that exceeds the capabilities of the USB port will run at a lower speed. For example a USB 3.0 device will run at USB 2.0 speeds on a USB 2.0 port.

Sort

add arrow-down arrow-left arrow-right arrow-up authorcheckmark clipboard combo comment delete discord dots drag-handle dropdown-arrow errorfacebook history inbox instagram issuelink lock markup-bbcode markup-html markup-pcpp markup-cyclingbuilder markup-plain-text markup-reddit menu pin radio-button save search settings share star-empty star-full star-half switch successtag twitch twitter user warningwattage weight youtube