Well, John, regarding the Copper and blitter not being able to do anything on
their own, (and I know that this is a somewhat trivial example), there is an
implementation of Life that is exclusively copper list commands that happens to
be one of the fastest implementations of the program anywhere. While this runs,
the system continues to run, and the copper can continue to service display
requests on an interrupt priority basis. Sounds like multiprocessing to me.
Now, there is no reason that a similar, coprocessor-specific application cannot
be written, such as fractal displays, to be run while another part of the
program is specifically written to the 68K CPU.
–Gabe