The Z80 might be decades obsolete and a few years out of production, but it’s absolutely a case of “gone but not forgotten” in the hacker world. Case in point is SymbOS, a multitasking OS for Z80 machines by Amstrad, Sinclair, and the MSX2 family of computers that updated to version 4.0 earlier this year.

The best way to describe SymbOS is like looking at an alternate reality where Microsoft created Windows 95 ten years early to put on the MSX instead of the BASIC they were paid to provide. SymbOS 4.0 comes even further into alignment with that design language, with a new file explorer that looks a lot like Windows Explorer replacing (or supplementing) the earlier Midnight Commander style utility in version 3.

Thanks to the preemptive multitasking, you can listen to tracker music while organizing files and writing documents, and even play a port of DOOM. Chat with your friends on IRC while watching (low res) videos on SymboVid. If you’re looking for productivity, all the old business software written for CP/M can run in a virtual machine. There’s even an IDE if you can stand the compile times on what is, we have to remember, an 8-bit, 1980s machine. It’s hard to remember that while watching the demo video embedded below.

The operating system supports up to 1024 KB of RAM (in 64 KB chunks, of course) and file systems up to 2 TB, which is an absolutely bonkers amount of space for this era’s machines.  One enterprising dev has even got his CPC talking to ChatGPT, if that’s your jam. You can try SymbOS for free online on an MSX emulator, or toss it onto a spare Raspberry Pi.  If you’re feeling adventurous, there’s a port in the works for the Isetta TLL retrocomputer.

This isn’t the first modern OS we’ve featured for the Z80, the processor which will live forever in our hearts and tapeouts.

Thanks to [Manuel] for the tip.

The ZX Spectrum is perhaps most fondly remembered as a home computer and a games machine. [Tito] has grabbed the faithful black plastic box and turned it into a frequency counter as an innovative entry to our 2025 One Hertz Challenge.

The code was prepared in assembly using ZASM—a Z80 online assembler. It works in quite a simple manner. The code runs for one second at a time, counting rising edges on the EAR port of the ZX Spectrum. Those edges are added up to determine the frequency in question, and the job is done. [Tito] has tested the code and found it’s capable of reading frequencies up to 20 KHz. Since it runs on a one second period, it’s thus eligible for entry by meeting the requirements of the One Hertz Challenge. Code is available on Github for the curious.

The ZX Spectrum has a clock speed of 3.5 MHz, meaning it’s not exactly the tool of choice if you’re reading faster signals. We’ve seen similar done before. In any case, this project was a great way to exercise assembly coding skills and to bust out some classic Speccy hardware—and that’s always a good time. If you’ve got your own retrocomputer hacks brewing up in the lab, don’t hesitate to let us know!