Third-party USB hubs may incorrectly disconnect after wake from sleep, causing system instability
Some third-party USB hubs and devices connected though them may disconnect unexpectedly after the computer is woken from sleep. This may cause unexpected behaviors such as general system instability within open applications, or data loss if a connected device was being used to store data from an open document. If a printer was connected through the third-party USB hub, it may not be recognized.
This behavior will only occur if the following conditions are met:
- The third-party USB hub doesn't support the proper USB wakeup sequence.
- The third-party USB hub is connected downline to another USB hub. Note: Apple displays containing USB ports are considered to have a hub, so if you connect a third-party hub to the display, then that USB hub is considered downline.
- The computer is woken from an external USB device such as a mouse or keyboard.
The problem can be avoided by doing the following:
- Connect all USB input devices, such as mice and keyboards, directly to a USB port on the computer or to an Apple display that is connected directly to a USB port on the computer.
- Press the power button on the computer to wake it up instead of using an input device that is connected to a third-party USB hub.
- Connect USB storage devices directly to a USB port on the computer to prevent third-party USB hubs from affecting them.
For more information on third-party product specifications and features, contact the manufacturer of the device.