[Coco] hardware port mapping question

[Joel Ewy]

Roger,

If what you're going for is a CoCo network, you might want to take a
look at Jon Bird's DragonNet/DNOS stuff: 
http://www.onastick.clara.net/netwrks.htm    He built some simple
network interface cards for the Dragon that use 6850 ACIAs (schematics
on his web site) with ROM-based software to emulate DragonDOS
functions.  His network is token-based, which is how he avoids
collisions.  But he has [some number >2] computers connected by a single
pair of wires.  One Dragon is the server, which manages the token.  It
hooks up to another Dragon running OS-9 over a parallel link, and others
running BASIC, which are diskless clients, accessing all mass storage on
the server by means of the network.  So part of the network is parallel,
using 6821s, but most of it runs off a single pair of copper.

A while back I was interested in doing something like what he has done. 
I emailed him and he sent me the source code for the OS-9 portions of
his network software.  He didn't have the source for the DragonDOS
components anymore.  Unfortunately, the server, which sends out the
tokens, was DragonDOS only.  (I think the binaries are there, so they
could probably be disassembled.)  However, the OS-9 stuff includes
well-commented source for a proper NBF file manager, SBF file manager,
ndisk device driver, net6850 driver, sbf6821 driver, network device
descriptors, OS-9 file server program (still needs something else to
manage packets and route information around), and even sysgo and boot
modules for booting OS-9 from the network on diskless Dragons.

All told, it's pretty impressive work, and it seems well documented
enough that re-implementing the stuff for which he didn't have source
(which wouldn't have worked unmodified on a CoCo anyway) should be quite
doable.  My idea was to implement all the packet routing and token
management in (Nitr)OS-9, so you could have a single OS-9 system as the
master server for the whole network.  What a good use for an old CoCo 2
-- stick a hard disk on it and let it serve files.

Anyway, if there's interest in this stuff I can upload the source to the
usual FTP sites.  I think Jon's done a lot of good work, and I got the
feeling that he would be happy to see it ported to the CoCo.  Even if
the eventual results are fairly different from Jon's original DragonNet,
he's got a bunch of great source code which would make a good starting
point for just about any kind of CoCo OS-9 networking.

JCE

Roger Taylor wrote:
> This relates to a very interesting project I want to attempt if it's
> possible.
>
> What I'd like to do is connect 4 CoCo's to each other via ribbon
> cables between all of the expansion ports.  On each CoCo I'd like a
> dip switch (or maybe just hard-wired) that sets the CoCo # to 0-3 and
> let each CoCo see each of the others 8-bit data port in a block of
> ports starting from some free address.
>
> An example:
>
> 65384 CoCo A
> 65385 CoCo B
> 65386 CoCo C
> 65387 CoCo D
>
> I realize 65384 is reserved for the RS-232 pack, but I'm just using
> the address as an example.
>
> Each CoCo would map those addresses and see 8 data lines from the
> other CoCos.  Can this project be put together with just ribbon cable
> and a few soldered-in components for each CoCo board?
>
>
>
>
>