Breadboard Colecovision

The Colecovision was a state-of-the-art game console back in 1983. Based around the Z-80, it was almost a personal computer (and, with the Adam add-on, it could serve that function, complete with a daisy wheel printer for output). [Kernelcrash] set out to recreate the Colecovision on a breadboard and kept notes of the process.

His earlier project was building a Funvision (a rebranded VTech Creativision) on a breadboard, so he started with the parts he had from that project. He did make some design changes (for example, generating separate clocks instead of using the original design’s method for producing the different frequencies needed).

Of course, a modern ROM is larger than the original designers had available. [Kernelcrash’s] build originally held 8 games in one ROM, but later enhancements upped that number even further. The redesign is interesting, but it is also illustrative to read about the stages of development and the troubleshooting it took to get it all working.

We’ve covered some retro console builds before. We’ve also had quite a few Z-80 projects on and off breadboards. If you want an overview of the Colecovision, along with some retro commercials, check out the video below.

Thanks for the tip [bunsenh].

13 thoughts on “Breadboard Colecovision

  1. I’d love to see a tear-down of that Zaxxon cartridge. That one game was 3D (an oblique side-scroller), and its cartridge weighed four times as much as that of any other game. Back in the day, I had theorized that it contained a second CPU. More likely, some kind of memory paging mechanism and a crap load of ROMs.

  2. It’s not hard to understand how CV worked but the video RAM address is a bit odd. If the schematic I found is accurate, the data input of each 1x64Kbit DRAM are connected to address. A0 to one, A1 to second one, A2 to third chip, etc. The data output goes directly to video chip and doesn’t connect to anything else.

    1. The video ram is accessed through the TMS video chips. It’s a strange way to do it if you’re used to say the TRS-80 or Commodore Computers. If you used the TI-99 then you would have a better feel for how the video ram is used in the Coleco..

      1. Sigh .. TI-99 .. TI seemed the undisputed ruler of “almost” in the micro world around that time. The TI 99 was almost good enough to break out, the TI-PC was almost compatible with the IBM-PC, had nicer graphics and somewhatniver hardware overall .. Almost good enough to break out from the crowd.

      2. Interestingly enough the TI 99 and the CV used the same video chip, and I think the same audio chip too. It’s as though they copied the TI schematic but dropped in a Z80.

  3. Interesting note in the blog on the Ali Express MB-102 boards:

    “Having bought a few of these MB-102 breadboards I am realistic that 1) for a lot of slow applications with a few chips they are fine and 2) that once upon a time some manufacturer made a really high quality version of these MB-102 things, then several Chinese manufacturers all cloned it, and tried to cut costs where possible, then cloned these again and tried to cut costs … until you have the world of today where you can’t tell if they are actually decent quality or not. I am sure ‘some’ of these MB-102 things are decent … but I have no idea which ones.”

  4. Ahhh, memories– anybody else remember buying ColecoVision PCB’s after the crash from JDR/Jameco for $2/ea? (and Adam keyboards and tape drives and power supplies…)

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