USB

The Axe-Fx II's USB support is Audio Class 2.0 compliant. The USB interface supports editing / remote control via Axe-Edit (no need for a MIDI interface), and can be used for audio communication (no need for an audio interface). Editing and recording can be done simultaneously. The Axe-Fx II can also be used exclusively as an USB-to-MIDI interface for other products (In the I/O > MIDI menu set "USB ADAPTER MODE" to ON).

• Mac: there's no need to install any drivers except for the firmware loader for the USB chip (it is a "soft" processor and downloads its code from the host on start-up).
• PC: Audio Class 2.0 drivers need to be installed.

The Axe-Fx II cannot connect to a USB stick. Source

Upgrading the Axe-Fx II firmware can be done over USB or via a separate MIDI interface.