The Z80 TV Game Powers Up Again

Few things are more exciting to a retro gamer than the discovery of an obscure gaming console from the past that they had not previously heard of. Whether it is the Vectrex, the Atari XEGS, or the Nintendo Virtual Boy, these discoveries open the door to some very unusual, and often very fun, gaming experiences. Those that have been around the digital block a few times may think that they have seen it all, but chances are that there are still some oddball consoles hidden in the recesses of gaming history.

Take the “Z80 TV Game,” for instance (yes, that is its actual name). It was never a commercial product, so it might be a bit of a stretch to consider it a lost console — but it does have a library of games to discover. It was first built as a homebrew project by a Mr. Isizu in Japan in 1987, and for the time, it was fairly powerful. The Z80 TV Game was equipped with a Z80 processor running at 4MHz, 16KB of RAM, and 8KB of dedicated video RAM.

Simplicity was the name of the game in designing the system. It consists of just 19 integrated circuits in total. It outputs a 60Hz composite video signal with 168x210-pixel resolution and 1-bit color. It also has 1-bit audio output, and a connector for a single controller. In particular, it was made to work with a Sega Master System gamepad, with its 4-way D-pad and two buttons.

For such a minimal system, the Z80 TV Game punches well above its weight. The machine’s architecture was designed around accessibility. Its address space allows for 32KB game cartridges, with the potential for larger titles through bank switching. The system’s ROM and RAM layout is straightforward: 32KB for the cartridge, 16KB for system RAM, and 8KB for video memory. This clear structure made it easy for programmers to understand exactly how their code interacted with the hardware, which also makes the console a great platform for education.

The console’s video sync signal isn’t generated by a dedicated graphics chip as you might expect, but by an EPROM to keep the component count low. The timing of the video output depends on the access speed of the ROM chip used, which means hobbyists sometimes have to experiment to find a chip that produces a clean, stable picture. The design also accommodates both Intel 8255 and Zilog Z80PIO I/O controllers for handling input and sound, allowing flexibility depending on which chip builders could find.

Despite being a one-off project, the Z80 TV Game has a surprisingly large software library. Mr. Isizu himself developed six original games, all written in Z80 assembly language, complete with commented source code. Modern developers have kept the platform alive thanks to tools like the Z88DK development kit and Inufuto’s Cate compiler, which make it possible to write new games in C. Using these tools, 20 additional games have been ported to the system.

Alex Lowry has developed a modern recreation of the Z80 TV Game and shared the schematics and design files needed to reproduce it. The components, like the Z80 processor, the memory chips, and the 7400-series logic chips, can all still be purchased new today, so go check out the details if you want to make your own version of this console.