So what /does/ it do?
It tries to force all screens to use a Productivity like mode (thus it needs at least a Super Denise or AGA). Once the software (which is called "VGA") is started it'll ask at every reboot which output to use, VGA or Amiga. In VGA mode, the screenmode preferences will not allow to select any other screen modes but vga. The hardware is just a switch between the two ports, without the software running it just passes through towards the DB23 port. Resolutions and number of colours are the same as with the Productivity mode: 320x480 to 640x960i. On ECS with 4 or 16 colours, on AGA with 256.
