Minstrel and ZedRipper - two very different Z80 projects

There’s a great blog here by Dave Curran about the successive design revisions of his Minstrel - a rebuild of the ZX81 using through-hole parts:

And for something completely different, here’s Chris Fenton’s story of implementing a 16-core Z80 token ring network on a $6k FPGA, with a mention of back-in-the-day offerings such as CP/NET and MP/M in the shape of Exidy’s Multi-Net 80…


I want that ZedRipper system in my house right now.

But serving 16 individual users (rather than a power user with 16 simultaneously running programs) sounds like the system I would prefer, with a terminal in each room of my house.

This is sexy AF.

And this is also when I evangelize that Gary Kildall should have been Bill Gates. IBM XT’s should have shipped with either his version of Concurrent (multi-tasking) DOS or Concurrent CP/M. Imagine how much further personal computing would be ahead now if IBM Compats were multi-tasking from day one.

Yes, I know we would still be trading a filthy rich billionaire for another, but Gary was a hippy so I believe he would have acted with more ethics that Gates. :smile:

Have you (has anyone here) got experience of running those Concurrent operating systems?

I see Wikipedia says this:

Digital Research also produced a multi-user multitasking operating system compatible with CP/M-86, MP/M-86, which later evolved into Concurrent CP/M-86. When an emulator was added to provide PC DOS compatibility, the system was renamed Concurrent DOS, which later became Multiuser DOS, of which REAL/32 is the latest incarnation

I have never used them. I’ve only seen them demoed on The Computer Chronicles.

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Over in the land of RC2014, Bill Shen has hooked up 3 Z80s and divided up the work of putting a Life onto an OLED screen. The Z80s communicate using dual port RAMs with built-in semaphore feature (although Alan Cox says there’s no need in this case for hardware support - the interprocess communication is simple enough to need only careful software design.)

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My Dad introduced me to the Concurrent PC Dos in the 80’s. I used Wordstar on it and the spreadsheet with 4 foreground tasks and a few background ones. It ran awesomely on my 286 at the time with an AST RamBank memory card (later changed to a BOCA)

It ran all my Dos applications… at that point I couldn’t tell the difference between a DOS app and a CP/M. Only after moving away to pure DOS did I realise that most of the things I used were CP/M

After concurrent and many years, I used DesQview as a multi-tasker on a 386 (It ran my BBS in one session)



I’m not sure I was even aware of it in my early PC computing days, else I would have run it. I did run CP/M on a Kaypro, but I had little knowledge of Gary, just that the labels I put into my 5.25 drives said CP/M 2.2 on them.