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by nickpsecurity 3695 days ago
"I'll give it a shot :)"

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"

http://www.learningaboutelectronics.com/Articles/D-flip-flop...

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:

https://en.wikipedia.org/wiki/Diode_logic

https://en.wikipedia.org/wiki/D-17B

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!

1 comments

Those resistors are not part of the flop, they're just there to limit current through the LEDs to make the state visible. See here for a D flip flop: https://en.wikipedia.org/wiki/Flip-flop_(electronics)#/media....

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.

I'll be darned. So, NAND gets some extra points on the flip flop. Far as analog, even if I ignored power rail we still have ADC's, DAC's, etc. This time I hesitate as I say I doubt they'll be implemented just with NAND gates.