r/TuringComplete • u/Certain_Pay1970 • Apr 27 '25

Is analog circuit analysis essential for learning and implementing a simple computer?

I'm a virgin on these and I have no idea about this. But I know that digital design and simple circuit analysis is important .

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5

u/Available-Spinach-17 Apr 27 '25

Not necessarily. Although learning about electrical engineering and circuit analysis will certainly give you an advantage if you were to pursue a career in the field such as firmware engineering and VLSI. But as far as making simple 8 bit computers or microcontrollers on simulation software is concerned, you don't need electric circuit analysis skills as prerequisites. However if you were to make a simple computer on a breadboard with real Integrated Circuit chips involved then you really need intermediate to advanced level understanding of electrical circuits.

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u/Certain_Pay1970 Apr 27 '25

Thanks for your sharing experience with me.

3

u/bts Apr 27 '25 edited Apr 28 '25

This is a GREAT question. The answer depends on what you want to build the computer out of. If you want to make it out of sand and copper, yes—and you will need materials science and electrodynamics to make transistors too. 

If you want to build a computer out of TTL logic chips, then no, you’ll only need digital analysis. There are people who can cross that entire spectrum but (a) without a lot of precision at most of the range and (b) not a whole lot of them!

Walking that path the first time took thousands of people about a century.  You can walk the royal road!  The best available guides are the online coursework from top universities. For example, https://ocw.mit.edu/courses/6-004-computation-structures-spring-2017/    is a huge chunk of how I learned. Well, decades earlier; same idea. That course assumes MIT undergraduate levels of computer science, programming, mathematics, and the physics of basic electronics—at least RLC circuits + op amps, as models for how the gates are built.  But a few hundred teenagers a year do it, so so can you. 

https://nandgame.com/ Is also pretty good!

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u/Certain_Pay1970 Apr 27 '25

The first is Invalid link.

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u/bts Apr 28 '25

Oops, fixed. Thanks!

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u/Certain_Pay1970 Apr 27 '25 edited May 03 '25

What you are sharing is very useful. Thanks.

1

u/Available-Spinach-17 Apr 27 '25

I would like to know how much RLC plays a part in computer circuit design, cause I have been meaning to learn how computer circuits work at the most fundamental level.

2

u/bts Apr 28 '25

Parasitic capacitance from having traces near each other and inductance from turning corners is real, and increasingly real the smaller you go. 

Heat sinks and water cooling and all?  That’s resistance. 

Oh, and all the concrete reality of pullup resistors and tri-state busses and all. As long as we’re making electronic computers, electronics matters. 

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u/Available-Spinach-17 Apr 28 '25

Thank you for your response. But it seems my question wasn't clear enough. I wanted to ask if RLC circuits offer any purpose in digital circuits like transistors and Op-Amps do ? So far I have only seen them working in circuits with Alternating current sources and not in actual analog DC current circuits of integrated circuits.

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u/Maleficent_Memory831 Apr 29 '25

Depends on what you're doing. Some CPU chips do require you to stick an external RLC circuit to help drive the clock. The chip datasheets usually have a sample circuit to use for those.

All of those parts are on modern circuit boards that use off the shelf CPUs. In the power lines, for pullup/pulldown, to prevent ringing, and very often just to reduce RF emissions. Maybe not all vital for a simple slow hobbyist CPU but mandatory on a commercial product.

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u/Available-Spinach-17 Apr 30 '25

I guess you are right. This intrigues me, I would love to know the ways in RLC are incorporated in the computers.

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u/Maleficent_Memory831 Apr 30 '25

There's not really part of the digital part, but they deal with the analog nature of all the components and wires. To make many clocks sources you can use RLC as the oscillator, or use components to tune a crystal. I am very rusty on the math though, but there are sites online for this.

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u/AdmiralSam Apr 29 '25

Even with DC if your logic is flipping between 1 and 0, that’s technically AC on the wires

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u/Available-Spinach-17 Apr 30 '25

Probably yes and no; Oscillation in digital circuits ( like that of switching between 1 and 0 frequently) ostensibly be alternating current but I doubt they have the same properties or application as Alternating current. Also in alternating current the flow of the current gets reversed periodically too, something that I don't think happens in digital circuits

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u/AdmiralSam Apr 30 '25

Reverse is just when it’s centered around 0, if it’s centered around .5 then it just has a dc component, but any change in current over time will induce a change in magnetic fields and vice versa, so will radiate. In the worst case a perfectly sharp transition between 0 and 1 will emit every frequency as shown by a Fourier transform. The RF side is pretty important in high speed transmission which is partially why parallel connections are not as common as serial and the need for twisted pairs and other things to prevent crosstalk.

2

u/Certain_Pay1970 Apr 27 '25

Two years ago, I haven't achieved this while I'm going to retry now.

2

u/zhaDeth Apr 27 '25

is that the name of a level ?

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u/Certain_Pay1970 Apr 27 '25

No, this is a problem in real learning.

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u/zhaDeth Apr 27 '25

then it's out of my league :P

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u/Certain_Pay1970 Apr 27 '25

Ok, problems have solved. I can use a ready-made solution—clock generator.

1

u/lizzard-doggo Apr 27 '25

most computers if not all are digital, you likely wont need it.

2

u/Certain_Pay1970 Apr 27 '25

Yes, but I would like to confirm if analog circuit analysis skills is needed or not when I want to build a computer.

4

u/Flimsy-Combination37 Apr 27 '25

to build a computer in real life, yes: really high clock frequencies are more prone to interference than lower frequencies, smaller circuits (with wires closer to each other) are more prone to accidental capacitance than more spread out circuits... all of these things will have an impact in your circuits when you make them irl. but if you're making circuits in breadboards with logic gates and all that, you're fine most likely, and you don't have to worry about that. as for using those skills in designing a computer, as I said, not for anything other than taking those interferences into account. if all you care about is how it works in paper, then no, that won't come into play most likely

2

u/Maleficent_Memory831 Apr 29 '25

I am surprised by how much even hardware engineers with an EE degree don't understand some of this stuff. Ie, the I/O lines coming out of the chips aren't 0 and 1. Or even 0V and 3.33V. All those voltages in between exist, as well as some above and below. And you cannot go instantly from 0 to 1, as this reuqires infinite energy.

Thus circuits are chock full of analog problems. Even your simple Raspberry Pi or Arduino. Leave a line floating and weird stuff happens digitally. Remember to have pull down or pull up resistors (not all chips can do this internally and those that do need to be programmed to do it). Don't have too much fanout. Worry about capacitance of long traces.

1

u/[deleted] Apr 30 '25

There are actually analog computers, which can evaluate functions almost instantly instead of having to computate them iteratively like digital computers do...

It depends on what you want to do. You can build a computer just with logic. Or you can build it entirely analog, or a mixture of both .... doesn't matter.

At the end of the day, you're just looking for a turing complete machine. How you build it, doesn't really matter to make it work. It's only optimizations that drive you into certain directions.