ECS stands for Enhanced Chip Set, the latest version of the Amiga's custom
chips that provides for improved graphics capabilities.  Some of the
special features of the Amiga's graphics sub-system such as the VGA,
Productivity and SuperHires display modes require the ECS.

 superhires (35 nanosecond) pixel resolutions 
 productivity mode 
 selectable pal/ntsc 
 determining chip versions