Comment by jstanley
5 years ago
If this gets you interested in z80 hardware, I would recommend building an RC2014: https://rc2014.co.uk/
I built an RC2014 after CollapseOS was posted last year, and thoroughly enjoyed it.
I ended up adding a front panel, complete with switches and lights, to allow toggling in and executing code without a ROM, and also wrote a HTTP/1.0 server for CP/M (which was an enormous headache for lots of different reasons). Never did get around to running CollapseOS on it though.
I love this project, and check in on it every few months. I particularly like the idea of scavenging hardware:
> With a copy of this project, a capable and creative person should be able to manage to build and install Collapse OS without external resources (i.e. internet) on a machine of her design, built from scavenged parts with low-tech tools.
I'd be interested in trying to build my own proof-of-concept, but my hardware experience pretty much starts and stops with kids' electronics kits from 20 years ago.
Assuming I can scavenge a Z80, what would be a logical next step? What books/other resources should I be reading to learn more?
Definitely read (at least the first chapters of) the Z80 cpu manual: http://z80.info/zip/z80cpu_um.pdf
It gets a bit dry when it gets to the bit that documents the individual instructions, but the overview before that point is well worth reading.
Once you've done that and you're trying to write code, this page is a good reference for the instructions: http://clrhome.org/table/
To build a scavenged machine, you'll need a Z80 CPU, a clock source (I think an RC oscillator would be the simplest working setup?), probably some sort of ROM, an SRAM, some sort of IO device (probably a Z80 SIO/2 for serial), and a 5V power supply. I think that should be all that is required. Then you need to load your code into the ROM at address 0.
Then you can connect the SIO to a USB serial cable (e.g. FTDI) and communicate with your Z80 using a modern PC.
I can't remember if the SIO/2 needs external address decoding logic, maybe you could cope without it if you are happy for it to use up every address?
But building an RC2014 would be easier and more likely to result in a working machine, and would give you almost all the knowledge required to build a scavenged one later if you still want to.
Thank you for your thorough answer. Especially when you frame it like that, the RC2014 sounds like like a fun next step. I'll definitely look into it.
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It is my belief that after civilizational collapse, a working macbook will still be much easier to scavenge than assorted parts such as a Z80, a memory controller, compatible memory, a writable EPROM for program storage, peripherals such as keyboard, video circuitry and a screen, and a power supply, nevermind much more useful.
Not too quite so, and the COS author addresses this in its website. (https://collapseos.org/why.html, section "There are two stages of collapse")
To be clear I don't necessarily share the view that this will likely happen, but for the sake of discussion I will assume it will.
A working macbook will indeed be much easier to encounter working at first, but not only is it much less durable (it isn't even particularly durable from current laptop standards), and parts are much more numerous, specialized, and hard to find. Macbooks in particular have a very tightly controlled supply chain, but this applies to other laptops too.
Z80 style processors and peripherals are still in use in various industrial and home appliance products, so it is still rather widespread anyways.
This means that while a laptop might be way more useful at the beginning of a collapse, it will probably stop being maintainable much earlier than a simpler computer will. In fact, if push comes to shove, it is plausible to actually build a Z80-compatible processor from discrete transistors.
> > a capable and creative person should be able to manage to build and install
> trying to build
What if there was a crowdfunding project to pay different people, to actually do this?
They could find unclear things in the docs, or missing docs. Usability Testing, sort of, of Collapse OS?
This is maybe pretty important after all :- ) More important than Fly-to-Mars rockets?