Another take on the 6502 computer


[Mark] is just starting off on his own 6502 computer odyssey. He was inspired by some of the other projects we’ve seen around here, like [Quinn Dunki’s] Veronica Project, but with a spin that leverages modern processors to alleviate some of the messy work. As you can see above, there’s an Atmel chip perched above the 65C02 processor. This chip not only feeds the processor data (through all those slightly diagonal yellow wires) but also provides the clock signal and operates the reset and bus enable lines.

This is more of a hello world post for [Mark]. The chip is simply running NOP commands right now. But it shows that the basic idea works, and the video after the break lets us see another time-saving aspect of the circuit. He’s using a character LCD to display memory location and data values. The plan is to get a blog going, which he’s hesitant to do as it takes valuable hacking time away from the project. We disagree. The write-up (although incredibly fun for us to read) ends up being a reference manual for him once the project starts to get really hairy.

17 thoughts on “Another take on the 6502 computer

  1. Maintaining blogs is something that is always troublesome for me as well. It isn’t bad when you are just working on stuff for fun or yourself, but when you have deadlines and obligations to others its sometimes a bit hard to stop and write what you just did in a blog post.

    1. The flip side of that is it can help motivate you when you’re stuck on a problem, and don’t feel like working on it. Knowing other people are awaiting progress is a good kick in the rump sometimes. :)

      I think you have to enjoy the writing process, though. If you don’t like to write, then the blog becomes homework, which nobody likes. Setting up RSS helps also, because it means there’s no pressure to stick to a posting schedule. My posts are sometimes weekly, and sometimes every three months, depending on my free time. But my readers are notified regardless and don’t have to check back all the time.

      It’s also worth noting that commenters on your blog can be very helpful. Several have spotted bugs in my code or suggested improvements to my hardware designs. I’ve learned a lot from them.

  2. I concur on Mike’s statement about the blog being useful. I refer back to my old posts all the time to remember how some bit is implemented. It’s like an online engineer’s notebook. The blogging saves me having to write this stuff down. Plus I get to make terrible puns on a regular basis.

  3. Hey Mark, I pretty much did the same thing as you a while back. In my case it’s a Z80 en I used a PIC16F877 to send code from the pc to PIC, which writes it to SRAM. The SRAM then functions as ROM, since I have no EEPROM programmer lying around. Maybe it could be useful for you in the future? Good luck hacking away :)

    1. This was my thought process after reading your comment:

      What kind of a hardcore nerd cares about the finer details of fscking jumper wires.
      Really, some people need to get some perspective or a girl or SOMETHING.
      Wow those are nice jumper wires!
      How did he get such nice jumper wires?
      No bending or kinking or loose connectors.
      Maybe I can get some to improve my USB front panel sp–WAIT A SECOND!


  4. I keep thinking I’d like to make another 6502 based machine one day and my old blog posts about my previous one are the only documentation I have on how I did it before. I am often referring back to my old posts to remember how things worked or how I did something. Especially when some of my projects literally take years to be done. The problem if you blog a lot is when you’re searching for something with Google you keep hitting your own posts but you can get around that using the -site: modifier on your search (e.g. I need to use that for a car restoration I am doing to avoid hitting my own blog posts on various topics.


  5. @HAD — “We disagree.”

    Disagree with what? – It absolutely takes time away.

    I used to host a blog for some projects I did, but found I spent more time doing that than the projects… which was partly why I moved away from doing it. I have considered going back to blogging, but haven’t yet because I know the time commitment it takes to make and maintain the content (and try to get attention paid to it too). I can understand this guy’s concern (at least at a glance).

    As a point of comparison, HAD doesn’t create original content or work through problems like this. Occasionally you have a one off tutorial article by your authors, but typically you just link to someone else’s content as opposed to taking the time to create your own. (been a loyal HAD reader for years btw)

    Not trying to sound harsh, but what HAD does vs. what you are encouraging this guy to do equates to apples vs oranges. Please at least be mindful of that before being judgmental that his decisions are not what you would do. You should be celebrating the content you capitalize on by posting it here… not questioning the motives of the people making it.

    1. each of the writers actually, in fact, has a blog of their own in which they document their projects. That isn’t the point anyway. The point was that we disagree that there’s less value in the documentation. We think the documenting process has value. Of course, we didn’t discuss this or anything, I’m just going by what Mike said in the article.

      1. Documentation is valuable even if no one else ever reads it too. I find for myself just writing something down helps set things straight in my own mind. To explain something clearly and concisely you need to fully understand it.

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