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Joined: Wed Aug 29, 2018 11:07 am
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I have always been interested in learning about low level computing. I've been working in the information technology and telecommunications fields for about 10 years now, but it's all been high-level stuff.

My ultimate goal is to build my own computer from scratch, but I have no idea where to start. I understand it's a daunting task, but it's my goal nonetheless.

Should I buy some sort of kit and start there?
Should I find some books on electronics or computer engineering? If so, any recommendations?

I've tried doing some searches on where to start, but either I'm searching for the wrong terms or the information is just that hard to find.

I'm very willing to learn on my own. Not looking for any handouts or hand-holding. I just need a place to start.

Any help would be greatly appreciated.


Wed Aug 29, 2018 11:17 am
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Joined: Wed Jan 09, 2013 6:54 pm
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Welcome! We're told that different people have different learning styles, so maybe a book is what you need, or maybe some video lectures, or maybe a kit to build with.

When you say "computer from scratch" I suppose you mean a microprocessor, and some ROM and RAM, and hook up a keyboard and screen? Possibly a good place to start is Grant Searle's projects. If you pick a 6502 project, then there's a healthy community over at 6502.org to help you. If you pick another CPU such as Z80, then the community at retrobrewcomputing might be a good place. We're helpful here, and knowledgeable, but we are not numerous.

If you want to understand digital logic, and address decoding, and so on, then Garth's primer is a good place to start - there are lots of links there to more resources.

Hope this helps!


Wed Aug 29, 2018 11:23 am
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Joined: Wed Aug 29, 2018 11:07 am
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Wow! Thanks for the quick response!

My initial thoughts regarding "building from scratch" were to maybe prototype something using a breadboard and other components and move on from there. I know I'm probably re-inventing the wheel, but I really want to understand how all this works. It has always fascinated me. And the only way I'm going to understand it, is to get my hands on it and see it work.

Thanks for the tips and references. I'll be checking those out!


Wed Aug 29, 2018 11:28 am
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Joined: Wed Jan 09, 2013 6:54 pm
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Sounds like a great way to start. Myself, I tend to read a lot. But my first computer was a kit, which I dutifully soldered up, and then re-soldered it because it didn't work, and then it did work. Understanding how it worked came in parallel and afterwards. So I do recommend building an existing design, especially something small and not clocked very fast, and then building on that experience.

It's certainly fine to build a system on a breadboard, especially if you take care with the power supply and the decoupling capacitors, and you run at say 1 or 2 MHz clock.

Garth's primer - and then, perhaps, searching on electronics stack exchange - will probably answer most questions about safe practices, and debugging. But do ask here, or on another forum, if you get stuck.

For myself, I read Horowitz and Hill which was a huge paperback. I still have it. You can get a copy for a tenner, and it probably doesn't matter too much which edition you get.


Wed Aug 29, 2018 11:36 am
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I can't tell you how excited I am right now! Thank you so much for the feedback!


Wed Aug 29, 2018 11:38 am
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Joined: Wed Jan 09, 2013 6:54 pm
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Do keep us posted, or let us know where you're posting your updates!


Wed Aug 29, 2018 11:40 am
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Joined: Tue Dec 11, 2012 8:03 am
Posts: 250
Location: California
BigEd wrote:
If you want to understand digital logic, and address decoding, and so on, then Garth's primer is a good place to start - there are lots of links there to more resources.

Thanks for the reference, Ed. actionfingers, most of my voluminous site is 6502-oriented, including of course the 6502 primer; but note that the primer also has a lot of material that will apply to most any other 8- or 16-bit processor as well. It is logically organized, and was written to address problems and questions that kept coming up on the 6502.org forum. These are the sections:

  1. Intro: Why a 6502?
  2. Address Decoding
  3. Memory Map Requirements
    plus: Why 6502 goes low byte first
  4. Interrupt Connections: IRQ and NMI
  5. 74xx Logic Families and Timing Margins
    plus: "Do I Need Bus Transceivers?"
    and: Static-Handling Precautions
  6. Clock Generation
  7. Reset Circuits
  8. What Do I Do With the "Mystery" Pins, SYNC, RDY, S.O., Φ1, MLB, BE, and VPB?
  9. Construction: Avoiding AC-Performance Problems
  10. Expansion Buses and Interfaces
  11. Getting More On a Board
  12. Answering Wire-Wrap (WW) Questions and Doubts
  13. What About Custom PC Boards?
  14. I/O ICs
    plus: extra info on 6551 ACIA clocking options
  15. Displays
  16. Where to Buy 65-Family Parts
  17. General Steps For A Successful Project
  18. Program-Writing: Where Do I Start?
    what to put in your .ASM file
  19. Debugging
  20. Tips For Programming the 65(c)02 (some affecting hardware design too)
  21. Basic Workbench Equipment
  22. Circuit Potpourri
Happy building!

_________________
http://WilsonMinesCo.com/ lots of 6502 resources


Thu Aug 30, 2018 8:45 am
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Thanks guys! I took a look at the primer and am currently reading "Understanding Digital Electronics." There were a few things you mentioned in your prerequisites that I was unfamiliar with. Namely, the points about 74-family logic ICs and their functions and the wire-OR'able open-drain or open-collector logic. I have no idea what those two items are referring to, so I'm hoping the books mentioned above will help out.

Thanks again guys!


Thu Aug 30, 2018 8:53 am
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Joined: Wed Aug 29, 2018 11:07 am
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I know it might be a little soon to be asking questions, but I'm stumped. Hoping someone can help me out.

I've been reading Understanding Digital Electronics. At the top of page 1-9, it gives an example where if scan line 9 is on and segment lines a,b,c,d,g,h are on, then the number 3 will be displayed. If scan line 9 is being turned on, shouldn't segment lines a,b,c,d,f,g, and h be turned on displaying a "9?" I feel like I'm missing something or that I'm not totally grasping the material.

Thanks in advance for any guidance.


Sat Sep 01, 2018 12:16 pm
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Joined: Wed Jan 09, 2013 6:54 pm
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Can you attach an image? It all sounds a bit confusing: '3' on a seven-segment display should need exactly five lit segments, and '9' should need six.


Sat Sep 01, 2018 12:25 pm
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Joined: Wed Aug 29, 2018 11:07 am
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Here's a link to the book.

https://archive.org/details/Understandi ... lectronics


Sat Sep 01, 2018 12:28 pm
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Joined: Wed Aug 29, 2018 11:07 am
Posts: 9
It threw in segment line h for the decimal point. That's why there's one more than it should be. But I still don't understand why there's a 3 being displayed when scan line 9 is turned on.


Sat Sep 01, 2018 12:32 pm
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Ah, I see. Note that there's a set of 9 lines for the nine digits of the calculator, and then 8 segment lines for the seven segments and decimal point. So, scan line 9 just means that the right-most digit is presently being driven. What they are not dealing with, yet, is how a '3' is represented, and how it is decoded to the pattern of segments.

Image


Sat Sep 01, 2018 12:43 pm
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Joined: Wed Aug 29, 2018 11:07 am
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Oh ok, I think I got it now. Thanks!


Sat Sep 01, 2018 12:46 pm
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Joined: Wed Jan 09, 2013 6:54 pm
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You're welcome! There was a very nice bit in a recent Intro on 6502.org:
Quote:
I then taught myself machine code from a magazine I had borrowed from an uncle. At first I didn't understand a single sentence from the article. But I believed it had to make sense one way or another, so I just kept rereading the article, probably dozens of times. Later I found out it was the 2nd article in a series and I had missed the introduction of all concepts.


I do like the sense of perseverance in that. Indeed, I bought a monthly electronics magazine as my own intro to digital logic, and I think similarly things didn't make much sense at first but reading more and more it started to. (I'd previously had an electronics kit with an excellent manual which had taught me a little of the basics of non-digital electronics.)


Sat Sep 01, 2018 1:03 pm
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