[ASipos]

Thanks, that page is nice, but it too emphasizes that you also need a clock. That's essential and it was the point I was trying to make. For example, a thing that is usually glossed over in OS courses (in favor of, let's say, scheduling algorithms and such) is that you simply can't make preemptive multitasking out of pure code - and later when you ask yourself how is it that such a phenomenon is possible in the first place you learn that chips are inherently parallel, that sequential code is an abstraction over that so that one can have some sort of law and order, and only then interrupts enter the scene so that one may break that order when needed, e.g. for preemption.

[jacquesm]

You can make a clock easily enough: two NAND gates, two resistors, two capacitors. If you use parasitic components you will get a pretty wild resonance so better to nail it down by using something a bit more stable. But in principle it will work just fine.

Agreed on the 'preemtive multitasking' bit, but that has little to do with this subject. And it is kind of embedded in the name, you need something to do the pre-empting which by definition has to come from outside.

But building a functional computer with just NAND gates is absolutely possible, even if there are better ways, just like you could use Brainfuck or combinators to do meaningful computation. The whole idea of the course is not to give some kind of purist model for computation but to show that the essence of a computer can be boiled down to some very simple building blocks. So the title of the course is misleading only if you want to pick nits. Course titles are made to attract students and to give broad cover to what the course is all about, not to satisfy language purists.

[goto11]

Couldn't you in theory build a clock purely from nand gates? You create a cycle of nand gates where the output of one is tied to both inputs of the next. If the cycle have an uneven number of nand gates, each nand will oscillate with a period depending on the length of the cycle.

[userbinator]

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

You can use NAND to make NOT.

[ASipos]

That's quite unexpected. Thanks.

[jacquesm]

If that's unexpected then I really find it hard to take your earlier comments serious.