Re: "Co-Processor" Apple ?

[mjmahon@aol.com (Michael J. Mahon)]

Robert C. replied:

>> "Michael J. Mahon" <mjmahon@aol.com> wrote in message
>> 20040806221648.23846.00003431@mb-m28.aol.com">news:20040806221648.23846.00003431@mb-m28.aol.com...

<snip>

>> > Check out parallel computing for 8-bit Apples on my
>> > Home page:  http://members.aol.com/MJMahon/
>>
>> Thanks, that's exactly what I wanted to hear. Now to do some reading on
>> "NadaNet".
>> ~Rob~
>>
>
>OK, I understand "NadaNet", and it is very interesting. I was wondering if
>it would be possible to interface the two Apples via the expansion slots,
>using the data and address buses, and the interrupts (IRQ), to halt each
>other. The details and how or who will control what are still undecided. Any
>ideas?

Sure, anything is possible.  ;-)

But that doesn't mean that it's easy, or that it will work as fast
as you want or be as compatible with other software as you want.

A minimal approach would involve at least latches on each bus,
with a handshake line or two, possibly interrupt-driven.

The simplest way to proceed would be to use a bidirectional parallel
port card--say, something with a 6522 on it, and use the 6522 to
both control the handshaking and the IRQ line.

Care would have to be taken to ensure than only one card was ever
driving the data lines, so arbitration would be a software issue--unless
you decided to go pure master-slave (which is also a software resolution).

Assuming no DMA hardware (much more complex), the speed of a
parallel port connection controlled by software would be in the range
of 50KB/second--about six times faster than NadaNet in raw speed.

The real question is what you want to do after you get the Apples
communicating.  Maybe you should give NadaNet a try to prototype
your applications...  ;-)

There's a lot to be said for interfacing through the game port.  ;-)

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/