[Coco] An FPGA GIME project, and CoCo FPGA Experimenter's Board

Zippster zippster278 at gmail.com
Wed Oct 21 21:28:02 EDT 2015

Hi guys, these are a couple of cross posts from the Facebook group for people on the mailing list that don’t use Facebook.
I’m planning another project to follow the MC6847 FPG VGA boards, and there’s been a little discussion over there.


I've started doing some of the prep work for an FPGA GIME chip replacement project. This is a stepping stone toward a CoCo4 project.

What I'm planning on is to develop a drop in board for the CoCo3 that will implement a GIME in FPGA, with 2MB of static RAM, and direct VGA out.

I'll be using an Altera Cyclone IV FPGA for the project. Since more I/O pins will be needed than are available on Cyclone IV QFP packages, this is going to require me to use a BGA256 packaged FPGA and a four layer PCB. Toward this end I have a reflow oven on the way, and I'm entering the needed parts into Eagle. This will give us quite a few pins to work with in implementing new features later.

This is going to be a very interesting and challenging project in several ways, but it's the big missing part of the puzzle hardware-wise to a fully CoCo3 compatible CoCo4, so hopefully it will be worth the effort.  :)


As I've been entering parts preparing for the FPGA GIME project, I had an idea. With the work I'm having to do for that project, it would be relatively easy to develop an "FPGA Experimenter's Board" that would plug into the CoCo cartridge port along the way.

Kind of an FPGA development board that could be used for interfacing projects. With an Altera device, some bi-directional level shifters, maybe an ADC chip, a couple of resistor DACs, and some other support circuitry, we could have a pretty cool board for people interested in CoCo/FPGA projects. Maybe help get some more hardware developed.  :)

Is there enough interest in something like this for me to pursue it on the way to doing the GIME replacement?

What do you guys think?

- Ed

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