Accessing the Early Boot Screen:
The Amiga Early Startup Control Screen allows you to select Boot Options, Display Options, or Expansion Board Diagnostics.
Access the Amiga Early Startup Control Screen by turning on or rebooting your Amiga while holding down both mouse buttons.
You can toggle between NTSC and PAL display modes by pressing any key on the keyboard, except for the qualifier keys (Shift, Alt, and Control) and the cursor keys.
Exit the Amiga Early Startup Control screen by selecting the Boot button for a normal system boot or the Boot with No StartupSequence button to boot directly into an AmigaDOS Shell window.