The retro pinout project

The retro pinout project

One of my main goals in sharing retro computing is to help people DO things with these machines. They are useful for all sorts of reasons, not the least of which is education and demonstration. The constraints are wonderful for this.

Using 30-50 year old hardware comes at a price. They are, well... old.

They require constant care and maintenance and parts are becoming more and more scarce.

Enter the retro pinout project

In fixing or maintaining these old computers, one of the best resources you can have is a similar working model next to it. Being able to test things out on a working example is invaluable.

Last week I was perplexed by the output I was getting on a "black screen" machine.

My friend Charles sent me a picture of one of his boards scope output on the same pin:

This DRAMATICALLY shortened the time I spent chasing down the problem. Knowing what a good output should be proved invaluable.

The next best thing is documentation and some accompanying examples of what things should look like when they're operating normally and when they're not.

Many of us use the Pictorial fault guide in the Commodore world to start to narrow down what a particular problem might be.

I decided to start collecting this data and figured it might be useful to others as well.

Here are a some examples from a VIC-20 (PAL CR Board):

Pin 39 of the CPU, verifying the clock output
Pin 23 of the CPU, a normally running address line

Open to contributions

I don't actually own all of the computers I'd like to see this information gathered for so I've put the project up on Github.

If you don't want to mess with git, please just email me ( and we can work some way for you to contribute your machine's examples.

At the moment in work are:

  • VIC-20 PAL and NTSC CR Boards
  • 64C PAL
  • 64 Breadbin 250407 NTSC
  • 128 NTSC

Highest priority that I'd like to see contributions for are:

  • All other Breadbins
  • 64C NTSC
  • VIC-20 9V Boards
  • All PET Models
  • 128 flat or D PAL

All contributions are welcome of course. I also have this idea to hold examples for the other 8 bit lines of computers like Atari, Sinclair, Amstrad, Tandy, etc.

What do you need to contribute?

A working example and an oscilloscope. I don't think it's necessary to have a fancy scope, but if you're taking a photo of a scope screen, it's a good idea to then include some information like scales your machine is set at. This could be in a text file. The information is more important than the format.

Problems you can help solve

Some pins like the chroma/luma output on a VIC chip are hard to visualize with a frozen in time scope screenshot. These are better observed over a few seconds. I'm looking for suggestions on how to best capture these. I'm leaning towards simple formats, possibly gif that will be around (or at least usable because of their openness) in 40 years.