The custom chips have been revised as the amiga platform has evolved and
newer models of the Amiga developed.  The latest revision of the Amiga
custom chips is known as the Enhanced Chip Set, or ecs.  certain features
of the Amiga operating system, such as higher resolution screens and
special genlock modes, require the ecs version of the custom chips.  in
this book, features that require ECS are noted in the accompanying text.
For more details about the special features of ECS, see appendix c of
the Amiga Hardware Reference Manual.