Re: What are the chances of a Replica II project?

["Michael J. Mahon" <mjmahon@aol.com>]

Chris Morse wrote:
> Question is, would it be legal to implement?  Would it be much more
> difficult to implement?

A little more difficult, but similar.

> > From a legal standpoint, I would assume the ROMs are off limits.
> Though if you own an Apple II already, would it be illegal to use them
> in your own electronic designs?

What is strictly "legal" and what is acceptable for people to do in
the privacy of their own homes are sometimes different.  ;-)

> Modern computer systems are ill-adapted to learning about computers,
> especially the hardware-related aspects.  Try to design even a simple
> board for todays PC architectures.  It would be nice to have a modern
> kit for an 8-bit computer system (like the Replica I) that was
> functionally equivelant to a real system (ie, the Apple II.)  I think
> from an electronics hobbiest/student point of view, it would be more
> exciting to build a computer system for which there was already a
> plethora of knowledge and information on.  Candidates for such a system
> would be an Apple II, C64 and an old IBM-PC (ISA bus).

Finding a *real* Apple II+ is still not hard--though collectors are
making it harder.   II+ clones may actually be getting easier to find
than the real thing!  But they certainly qualify, since they are usually
100% Apple II+.

> Yesterday I dug out an old book called "The Apple Connection" by James
> Coffron.  Even from my limited electronics background, it doesn't look
> very complicated to use the Apple II system bus.  In chapter 4 (Input
> and Output Hardware for the Apple), I think he does a good job of
> describing the Apple II's 50-pin I/O slot and how the signals are used.
>  By the end of the chapter, you've designed a basic Apple II board with
> 8 LED's that you can turn on/off with PEEK/POKEs.  But I would be
> pretty timid the first time I tried to insert a home-made card (even a
> simple one) into a working Apple II.  I'd hate to start frying real
> Apples..

The Apple II peripheral bus is perhaps the easiest bus to interface
to in any personal computer.  It provides slot select decodes,
dedicated slot ROM space, expansion ROM space, several clocks...!

> The Replica I has an expansion port, but it's completely different from
> the Apple II design slot design.  With a "Replica II" type of project,
> boards designed for such a machine could be plugged directly into a
> real Apple II.  Nice.

The Apple II peripheral bus was designed as a leap in expandability
and ease of use.  Truly the first real example of "plug and play".
I, too, consider implementation of the peripheral bus as a necessity
for any modern replica.

Most "replicas" that are being discussed are not TTL replicas, which
would be easy to probe and understand, but are FPGA replicas, in which
the machine exists entirely within one chip, as "source code" for the
logic equations.  I leave it to you to decide which is more transparent
for your purposes.

-michael

New, faster SUDOKU v2.0 solver for Apple II's!
Home page:  http://members.aol.com/MJMahon/

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