Garbage output on USB serial terminal

All firmware burnt to my Dan Dock M1 results in garbage output at the USB serial terminal. Take the hello_world example, the output looks like

$ python -m serial.tools.miniterm

--- Available ports:
---  1: /dev/cu.Bluetooth-Incoming-Port 'n/a'
---  2: /dev/cu.YuchisBeatsSolo3-SPPSer 'n/a'
---  3: /dev/cu.YuchisBeatsSolo3-Wirele 'n/a'
---  4: /dev/cu.usbserial-1430 'USB2.0-Serial'
---  5: /dev/cu.wchusbserial1430 'USB2.0-Serial'
--- Enter port index or full name: 5
--- Miniterm on /dev/cu.wchusbserial1430  9600,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
(␀

Note that each time I reset the board by pressing that button, the output would change, but its length remain fixed. I have overclocked it to 600MHz in a previous experiment, and I wonder if that has somehow damaged the board?

don’t you need to provide some arguments with miniterm? Such as the device and baudrate (probably 115200 instead of the default 9600).

It works! Thanks for the baudrate tip!