[Coco] CoCo/PC hybrid....

Frank Swygert farna at att.net
Tue Sep 15 16:53:26 EDT 2009

It should be fast enough to send/receive commands for something like a 
relay board too. I've seen a relay or generic I/O board for a parallel 
port on a PC before. I'm looking at the maximum use of existing, 
inexpensive hardware. Even a P4 small form factor computer goes for 
under $200 with 512MB and a 20-40GB hard drive. Drop to a standard 
Pentium or a P2/P3 class processor and it's even less -- but running a 
DOS based CoCo emulator from flash memory or a USB drive would make even 
a P1 one heck of a fast CoCo! Once that was up and running we could look 
at expanding the capabilities of the hybrid machine to create more or 
less a "CoCo4". That is if we can get the source code to one of the DOS 
emulators, or the author to tweak it some. I'd think it should at least 
have a CC2/3 mode, even if the advanced capabilities had to be locked 
out, even if it required rebooting the system. I still like the idea of 
having it boot up to a simple menu screen that had several options, one 
being the capability of creating a real CoCo disk (provided an 
acceptable drive is present) and transferring files. Would be even 
better if CoCoNet or Drivewire were built into the emulator.

I'd really like to see SECB expanded as well as OS-9 capabilities, only 
because SECB is so easy to program. The only problem is any expanded 
functions would only work on the "CC4", but if the "CC4" concept 
described above could be packaged on a "live cd" like some Linux 
distributions (oh if it could be done with a small linux instead of 
DOS!!), or on a USB drive, then there should be no problems. Nitros 
would just need some new drivers...

jdaggett at gate.net wrote:

EPP interface is used in configuring FPGAs. So being able to send and 
read data from a ROM cartridge should not be all too tricky. Only thing 
if I remember correctly EPP/ECP port speed in not all that fast. Still 
fast enough to move it from the cartridge to a virtual ROM in a PC.
An interesting idea.


On 14 Sep 2009 at 21:44, Frank Swygert wrote:

  Okay, I never have been much of a programmer, and really done little 
more hardware than a few kits and mods to existing hardware, but I've 
been thinking too much!

One of you programming guys take a look at the resources on this site: 
I've been comparing the pin-out of a parallel port to that of the CoCo 
expansion port. I'm almost convinced that it would be relatively cheap 
and easy to make a small converter board that would plug into a standard 
parallel port and take a CoCo cartridge. Might have to add a source of 
external power, but that could be a cord that goes back into the PC case 
and plugs into a drive connector. Hey, even move +12V out there! The 
goal would be to use cartridges for data transfer purposes or to 
build/use an inexpensive I/O board. Throw the cartridge compatibility 
out and just make it a multi-purpose/experimenter's I/O board with a 
wire-wrap header and I think it gets cheaper and easier. Limit the goal 
to a data I/O board that could be programmed from Nitros9 or DECB and 
forget the cartridge connector and things get easier!

The real headache I see is the 13 address lines. There would have to be 
some kind of decoding done on the board so that only a couple lines on 
the parallel port could be used for decoding. But then again if you 
throw away direct cartridge compatibility and use it strictly for data 
I/O, is that much address decoding really necessary? Told you I wasn't 
much of a programmer/hardware builder!!
Programming the port from DECB is my main interest. One thing I always 
liked most about the CoCo was the easy I/O projects and using it as a 
controller. Started to write a digital dash for my car using just the 
serial, cassette, and joystick ports for inputs (mainly the relay on the 
cassette port). Lack of an inexpensive display easy to install in the 
dash stopped me! There are such animals for cars now, but that 
programmable I/O port would sure make a CoCo emulator customized and 
installed in flash memory on a simple single board computer (maybe an 
inexpensive Mini ITX with a VIA 800MHz chip...) a real possibility. The 
older Mini ITX boards are starting to show up on e-bay priced reall 
nicely. Would make a good base for a "CoCo4" (didn't want to use that in 
the subject line though!!). Use a IDE to flash card adapter for the main 
drive, then attach a small IDE laptop drive....

Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
(free download available!)

More information about the Coco mailing list