Tuesday, 10 May 2016

By popular demand - my Coco3 setup

I've been inundated with requests (at last count, at least 1) to show my development set-up. Of course all my coding and initial testing is done on my desktop PC using AS6809 and MESS, and no point showing that off. But I do have a few pictures of my Coco3 and shiny new CocoSDC.

CocoSDC Floppy Disk emulator

The CocoSDC allows you to simultaneously use real floppy drives (via an MPI), disk images on a DriveWire server (eg. PC), and of course the disk images stored on the SD card. At the moment I'm just writing the Space Invaders disk image to the SD card each time, but for extended development-test cycles it's much more convenient to use a DriveWire cable (I can't find mine atm). For anyone interested in finding out more about this piece of hardware, here's the link to the homepage.

The perspex case was a limited run. I'm glad I bought one - a year before I even owned a CocoSDC - I think it looks pretty neat!

Coco3 running Space Invaders from the CocoSDC

And here's my Coco3 set-up, balanced on the edge of the desk amid a rat's nest of cables. It's an '87 GIME with a Cloud-9 512KB upgrade, using low-profile SIMMs that were pulled from classic Macintosh machines. One day I'll swap it for a Triad. I'm having trouble finding a display that will work with the Coco; I've commandeered the kids' TV which was stored away for a few weeks whilst the wife paints the playroom, so I'm living on borrowed time in that respect.

There's the obligatory Dilbert mug of course, and to the right is my new EPROM eraser, atop which sits my sole remaining cartridge PCB and a handful of EPROMs that have been used to test Lode Runner, Knight Lore and now Space Invaders.

UPDATE: I've found the issue with interrupts on the real hardware! A temporary hack fixes the issue - just need to work out how to do a proper fix, and then I can release an Alpha!

UPDATE #2: Alpha release available for download.

The issue was related to GIME timer interrupts in MESS vs real hardware - seems there is a discrepancy. More details to follow.


  1. Truly very awesome! Thanks for sharing this!

  2. Great demo! Also love the set-up.

    Since I do CoCo 1/2/Dragon development, the emulation is better and I don't have to take it onto the real hardware as much.

    So, I mostly get by with A09, XRoar and MESS. When I want to put it on the real hardware, I usually use a cassette cable connected to my soundcard. I test with a real cassette deck at the end (although I have broken it and need to fix it...)

    I've also got a "MicroSD Drive Pak" for when I need some drive emulation.

  3. This is the 1st time I've had issue with real hardware, to be honest. So 1 from 3 isn't bad! Having said that, Lode Runner didn't use interrupts and I used a simple periodic timer interrupt in Knight Lore only for the RNG (that reminds me, I need to beef that up a bit).

    Cassette sounds painful... although as you say, it's not a frequent requirement.