Perhaps the saddest thing about the Zilog Z80 is that this humble 8-bit microprocessor wasn’t allowed to live until its 50th birthday. This, fortunately, doesn’t prevent people like [David Oberhollenzer] from reminiscing on this influential processor and what it means to them personally.

First released in July of 1976, this humble 8-bit miracle would go on to power not just a range of home computers, but also be found in everything from industrial controllers to arcade systems. Despite this success, the new owner of Zilog — Littelfuse — decided to put an end to this winning streak in 2024 for the stand-alone processor and its peripherals.

Although the original Z80 ecosystem ceased production, this didn’t prevent hobbyists from creating new operating systems for it, let alone entire new development toolchains, or demonstrate multitasking on the Z80.

Meanwhile, the Z80 architecture is still very much alive and kicking, such as in the form of the eZ80 SoC in the TI 84+ CE calculator that [grubbycoder] ported Sonic 2 from the Z80-based Sega Master System.

Among all of this modern-day Z80 goodness, we also have a few gems from the past to admire, such as the OS that Zilog made for this architecture in the form of Z80-RIO, which was sadly not as successful as the hardware.

Watching [sprite_tm]’s build of a handheld 486-based gaming computer, we got to thinking about retro computers and the eternal questions of how much of the computer needs to be actually “old” for it it be retro. Where is the soul of a retro computer? The CPU? The old yellowing plastic case? Maybe it depends on what you’re trying to get out of the hobby.

There is of course a spectrum of people playing around with old computers. For some people, let’s call them “vintage computer enthusiasts”, half of the fun is in keeping the actual old hardware running. This group tends to know what teletype lubricant smells like, and how to tell which capacitors need replacing.

For others, “team retro”, the joy is in using the machine itself, whether that be teaching the old dogs new tricks, or simply loading up nostalgic video games. Team retro is more content with emulations or emulations that are wrapped up neatly in hardware workalikes. They know which registers need POKEing, and whether or not Commander Keen is running at the right framerate.

I think [sprite_tm]’s project falls in with yet another camp, the retro-reengineers. Here, the idea is to step through the engineering lessons of the past by re-designing something from a bygone era. So when [sprite_tm] went with a period 486 CPU backed up by a modern FPGA, perhaps ironically borrowing code from the modern MiSTer project, it makes sense for his goals. Retro-reengineers know the bus architecture and the memory timings, and they are reinventing the wheel as a learning experience. Or in the case of [Voja Antonic]’s imaginary four-bit machine, it’s a teaching experience.

How you work often reflects what you’d like to get out of the project, and at Hackaday, of course, we love all of the above! We’ve identified at least three broad schools of fooling around with old computers. Are we missing any?