Force OS X to use Bluetooth dongle instead of built in controller I'm using a Magic Mouse with my MacBook Pro and Mountain Lion. The cursor sometimes start to lag. I figured, the reason for this could be the distance between my Mac and the mouse (about 1.5 meters / 5 foot). 

I bought an external USB Bluetooth dongle I want to plug into my monitor on my desk, so the mouse is closer to the controller. However, I can't figure out how to make OS X use the external dongle instead of the built in controller. 

When I go into System Prefs > Bluetooth and hold the Option key to display the reception, I see that it is the strongest when it's next to my Mac and not when it's next to the dongle. So what can I do to change that? Thanks!
To force the system to use USB Bluetooth dongle by default, run the following command:

sudo nvram bluetoothHostControllerSwitchBehavior=always


This will modify your boot kernel arguments.

To do opposite, use never. The change would be applied after the reboot. To return to the default, run:

sudo nvram -d bluetoothHostControllerSwitchBehavior