This is how you do homebrew CPU's and presentation best:
Links to others for anyone wanting to learn about this stuff:
Only thing was that a HW guy told me the TTL chips he used might be hard to come by. I looked them up and had trouble finding them. So, rather than cloned, the next Magic 1 should be ported use components currently available... preferably 10 year horizon. Also, ideally something fabbed at 0.35 microns or above for visual inspection. Plus realism, as we're practically cheating if you're using deep submicron for "hand-built, old-school" systems.
What kind of primitive components are you using or found consistently available?
"hey kid, I built one of these too, back in the day, and it was damn hard and time consuming, but oh a labor of love. I had no internet, nor any schooling. I read articles in Popular Electronics and I read the TI 7400 series databook. Then I reread them. Then I reread them." Yes, in fact it was snowing, uphill, and I in fact had no shoes!
To answer your questions, it's hard wired with the control logic made out of the simpler chips (7400, 7408, 7432 etc) but the rest of the system does contain more complex chips, the 74181 ALUs being the largest.
I know that the author was being sarcastic, but really, 4MHz with 32kb of RAM is like state of the art 80's technology. The fact that we are even able to get to this point with protoboards and discrete off-the-shelf logic chips is impressive.
I mean, I learned how to program back in 1988 in a computer not much more powerful than that.
logic cells: easy, by universality of NAND.
RAM: distinction between flip flops and RAM is unnecessary from a strictly technical standpoint. a massive (or not so much) array of flip flops with decoder and mux (also just made of NANDs) can get you by.
ROM/flash: maybe I could argue NAND flash counts as just a NAND gate, but not quite. I'll concede nonvolatile memory with just plain old NANDs. May I suggest a https://en.wikipedia.org/wiki/Diode_matrix?
"analog components": having Vcc and ground available is an implicit requirement of having a functional NAND gate, and IO could just be some wires mirroring a memory location.
Overall I'd say its a largely accurate statement. All you need is something to set up your initial conditions (e.g. program in memory).
Things We Actually Did:
Mercury delay lines were tubes full of mercury we sent vibrations through. Those vibrations would reflect around and get detected and read out later. This wasn't, technically, random-access, but it was memory.
Williams-Kilburn tubes were CRTs with long-persistence phosphor, the exact opposite of what display CRTs used, and metal plates on the front to allow the contents of memory to be read out. You could have two identical CRTs, one with the plate to use as RAM and one built into the display panel so the operators could see the contents of RAM in real time.
Core memory was tiny little ceramic ferrite doughnuts woven into complicated metal grids which would change how they were magnetized in response to a sufficient current; their state could be read back out non-destructively, and core was, in fact, nonvolatile. The core modules were woven by hand by women working with microscopes and very steady hands.
Being able to make usable amounts of memory out of components we can just etch into silicon was an amazing advance. Nothing short of revolutionary, really; computers as we know them would be flatly impossible without cheap, plentiful RAM.
The rope memory I read about studying Apollo and Margaret Hamilton's work. Core I saw a bit of watching videos of Burroughs computers, my favorite, being assembled in factories. It was actually kind of mesmerizing watching that old stuff because you can see all the brilliance and intricacies of the device. Today, it's all hidden behind plastic for anyone except labs (eg ChipWorks) that can pull it out. People say, "Why would I pay (obscene amount here) dollars for this little piece of plastic?" One thing I do is show them pictures of old computers without covers saying "It's basically that... with 10x more components... squeezed into that tiny space. What, did you think squeezing a room full of wiring and components into a tiny space cost a few bucks?"
I admire your initiative. :)
"logic cells: easy, by universality of NAND."
Got me dead to rights there. Seems to be able to do anything boolean.
"a massive (or not so much) array of flip flops"
Close but still need the resistors.
"May I suggest a"
That's not a NAND gate but it's pretty neat. Thanks for that link. Especially as when you posted it I was, in search of esoteric constructions, just discovering and looking at these diode-based works:
Note: D-17B is pretty wild in design, appearance, tech, and reliability all at once. Makes me want to try it on 0.35 micron in voter part of lockstep or TMR circuits. :)
"having Vcc and ground available is an implicit requirement of having a functional NAND gate, and IO could just be some wires mirroring a memory location."
Now you're stretching. NAND doing signal conditioning, power regulation, or 2-3 component differential equations is hard to believe. I'm thinking it fails here. I admit I cheated by including an analog requirement but it exists in ever real-world computer (esp SoC) so it seemed fair-ish.
Overall, a high-scoring counterpoint that taught me some useful stuff about NAND gates and old-school ROM. I'm researching both reductionism and old-school techniques in anti-subversion hardware. So, quite relevant. Thanks!
My point was about Vcc and ground was just meant as a response to the "power-related analog components". If you don't already have a regulated power rail even a single NAND gate won't be able to do it's thing, so its definitely a requirement but if you say you are allowed a functional NAND gate you must be allowed power rails as part of that.
> In order to be able to program it at all, I wrote a very simple compiler (strictly speaking it’s actually an assembler)
Does that compiler/assembler run on your hardware?