On the subject of multi-processor systems, Mike Watson wrote:

>Synergy does not apply to multi-processor systems. You always end up
>with less than the sum of the parts because of the overhead of sharing
>data.

True, but don't knock multi-processor systems too hard.  I was the chief
software / firmware architect on a professional computer-based system with
a HUGE User Interface that uses up to 16 synchronous 8MHz Z80s (and an
asynchronous 16MHz Z180, which came later, to handle very-high-speed comms)
all running in parallel and sharing data via a tightly-coupled
shared-memory scheme.  10 years later, one can hardly believe that such a
simple $2 processor is behind 350+ $100,000+ such systems currently in use
around the world today ...

I think a major factor in the continued success and continual development
of that product was the common shared-memory interface and the flexibility
thereof -- it can handle large or small data transfers with aplomb,
inter-Z80 communications are a piece of cake, and additions to the
systems's functionality are usually trivial (except for the
ever-diminishing amount of free codespace available ;-) ).

Of course this flexibility required a lot of coding and code space, which
speaks against all but those PICS with the ability to execute from external
memory.

 ___________________________________________
| Andrew E. Kalman, Ph.D.   aek@netcom.com  |
|        standard disclaimers apply         |
|___________________________________________|