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The Z80 Membership Card

Last month, it was Wes putting together a retro-Pi project to run classic games from days past using emulation on the Raspberry Pi. This time it’s A Classic Retrocomputer Kit from the 1980’s. The idea is to build a classic Z80 computer to fit into an Altoids tin and call it a Z80 Membership Card.

Then in the 1970’s, the microprocessor was invented. Big companies viewed it as a primitive toy that could lure away customers and thus threaten their computing monopoly. But renegade groups of hackers saw it differently. Yes, it was a toy; but also a playground for unparallelled creativity, and a tool of unprecedented power. They sensed that the microcoprocessor was the next great invention that would change the world. The “lights” came on, the “wheels” started turning, and the “presses” quickly started churning out printed circuit boards that would revolutionize the world of computing.

These early microcomputers were pretty crude; like bicycles compared to sports cars. But that’s a good thing! A bicycle is vastly cheaper, and much easier to learn. Yet it can still take you anywhere a car can go, if you’re not in a hurry. And, a bicycle can take you to places that no car can ever go (with better scenery, too)!


The hobbyists that built them were often beginners and outsiders that didn’t know how computing was “supposed” to be done. They made their own rules, invented their own solutions, and came up with entirely new applications that were impossible with traditional computers. In the process, they wound up completely re-inventing the entire computing industry.

That was then. Hardware has changed but the ideas are still there. Build your own is a bit more sophisticated. Now you can build your own, too.

The Membership Card is a complete computer that fits in an Altoids tin. Inspired by classic 8-bit computers like the Altair 8800 and Heathkit H8, it is thoroughly documented and easy to build, with big parts, big pads, and big traces and spaces. It uses only generic parts common in the 1980s (and still available today) — no custom parts, and no surface mount. It’s fully self-contained: You don’t need PCs, Windows, megabyte compilers, or secret software to use it. Now you can learn about computers right from the ground up, and really understand how they work!

This is from the first era of the PC. That runs from the introduction of the first Apple and Radio Shack computers up to about 1982. That’s when the market opened up and the Commodore 64 picked up the home end (see the story in Distrita) and the IBM PC was struggling against Kaypro and Osborne and others for the ‘serious’ or business market. The second era in the mid 80’s was about a transition to disk based operating systems rather than ROM based. Hardware design and production improved dramatically and the competition was shaking out the loose leaves. 

The thing is, I already have several Z80 computers. Why build another? How can I use the ones I have? The TRS-80 Model 100 uses an 8085 and is an ideal size for a ham shack desk keyboard with a status display. The problem with these is illustrated by their serial ports. The RS-232 on these classic machines needed handshaking lines and carefully buffering even at 9600 baud speeds. The R-Pi handles serial communications at 115K baud without handshaking.

I am looking at the HP palmtops I have from the 90’s, too. There was a web site that was big on these a while back as there was a market for custom apps designed for them. The keyboards on these things was quite usable. The breaks in the case are probably the biggest inhibitor about trying to use the parts.

It is the keyboard and display that remain one of the biggest hurdles. When a modern tablet can be had for $50, retro projects lose some of any utility appeal they might have had. That just means that other motivations take the fore and that is a ripe field! There’s a lot of old hardware out there so the question is just what you can make with it.