Minimal 64 and TTL Breadboard Computer with Lego Paper tape reader

After finding different Gigatron TTL computers including a smaller Novatron
I found there the Minimal 64 Home Computer: The Most Computer from the Least Logic?

And there maybe even more of interest a breadboard computer with a Lego paper tape reader

there’s a playlist and some more YouTube recommendations like this nice TTL homebrew


Nice finds. Always found the Magic-1 to be magical! A machine which can host an editor and assembler is a special thing, to me, even more so than a machine with Basic. Best is to have all of them!

The LEGO tape reader is very nice indeed - looks like it is optical, 9 tracks including a central clock track, printed paper strips probably cut from A4 or so, and hand-pulled. Although this approach limits length a bit, it gets over the need to have a punch - an inket printer is enough. Nice to see the hand-typed 10 byte bootstrap, the tape with a decent loader program, and then a program tape.

Edit: it looks like Novasaur and Novatron are intended to be low-volume products from the inventor, not yet available. Not open-source but perhaps sufficiently source-available that one could do a self-build. Or, perhaps, buy as pre-production from him.

Edit: I find it very nice that Gigatron and derivatives live on, after the original inventor’s untimely demise.

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This crop of TTL computers, still use LSI chips for ram or rom or table lookup,
that lets them be Single Board Computers. This gets around the problem
having buses like MAGIC or TIME FRACTURE
and front panels, but does require things to 100% correct and no race conditions
in the logic or clocking issues.
PS: A true TTL era computer, would have 4 or 8 K ram per card of memory.


I was going to make the same comment as @oldben. One of the issues is that you cannot purchase anything like “retro” memory anymore unless you want to get expensive 40-year-old “collector” parts on eBay.

In my retrocomputer, I used the smallest, slowest, through-hole memory chips that are still widely available that I could find - these are 8k x 8 static RAMs from Alliance. Yet even these have 55ns access time. The the original 8k x 8 RAMs were, I think, 150ns, came out in the early 80s, and didn’t reach 55ns until (again, “I think”) the early 90s. This is like generations too recent for a true “retrocomputer”.

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I think this gives a glimpse through the kaleidoscope of retro-validity - each one of us, and each project, has its own sense of which choices are valid, whether it’s 5V operation, or through-hole parts, or period-appropriate silicon, or some particular microprocessor or some particular software environment. My own preference is to try to accept broad diversity - sometimes an emulation on a modern processor is very satisfactory, sometimes a green PCB stuffed with DIP chips is very satisfactory. And everything in between, can be good on its own merits, in my view.


I completely agree – and on top of this, our own sense of why we’re doing it and what we want to get out of it. On the subject of static RAM, for example, I understand and agree with you @pdxjjb, and it annoys me a little bit for my own work, but not a whole lot. Not a lot because I feel like handling dynamic RAM and its timings is a “solved problem” that I’m not currently working on, and handling chip selection is a “solved problem” that I’m not currently working on, so using a 55 ns 8 kB SRAM lets me compartmentalize and set aside the (comparatively) large cost and board area overhead of period-correct RAM boards to focus on other areas of system design. If I were trying to explore RAM access designs, or Woz up a wacky refresh system, or tinker with a system where wait states are the difference between correct and incorrect, I might feel differently.


Getting it working first is the main thing. I consider what I do is not true retro, but work alike
machines with similar timing and io. I tend to want to explore other options than the 8 bit byte
and the 32 bit float or long int.
A 8 bit byte plus 1 bit flag and 1 bit sign would make a nice memory for a variable length calculator type machine. Why go 64 bits when you can go 64K. :slight_smile: