Back to the future: Writing 6502 assembler with Amazon Q Developer
77 points by ingve 3 days ago | 47 comments
  • mxl9df 3 days ago |
    Interesting article, but the title is a bit off. "Assembler" actually refers to the tool that converts assembly language into machine code, not the language itself. So "writing 6502 assembler" would technically mean writing the assembler software, not writing assembly code for the 6502 processor.

    It's a small distinction, but surprising to see this mix up as assembly language enthusiasts tend to be sticklers for these details!

    • kjs3 3 days ago |
      I don't know anyone who doesn't say "I wrote X assembler" with complete understanding by all involved, and I definitely don't know anyone so pedantic they said "acksually, it's 'I wrote X assembly code'". I guess none of the dozens of assembly code makers or whatever I've know over the last 40 years was enough of a stickler. Or care one way or another.
      • rkeene2 3 days ago |
        I also understood the title to mean writing an assembler rather than writing assembly language code, and I've never heard anyone refer to writing assembly as writing assembler (or heard anyone who writes assembly referred to as an "assembly code maker", nor anyone who writes in any language referred to as an "<language> code maker").

        I could imagine such phrasing being done by non-native English speakers, of which I'm have no doubt that there are a significant number.

        My (unresearched) guess is that this is simply different dialects of speakers emerging with respect to informal references over the decades.

        • wtetzner 3 days ago |
          It seems to be pretty common even among native English speakers to use "writing assembler" and "writing assembly" interchangeably. If one were writing the tool that assembles to machine code, you'd say "writing an assembler".
          • PittleyDunkin 3 days ago |
            Normally I'd agree (as a native english speaker with about twenty years of writing assembly under my belt), but the title tripped me up, too. I figured they forgot an "an" or an "s" at the end of "assembler" and i was surprised to find that no 6502 assembler was produced. It could be because I've written three different assemblers over the last two years, though, so it could be i was just projecting my own interests.

            Still, I don't really care what it's called.

            • wtetzner 3 days ago |
              I actually prefer "writing assembly", and also think "writing assembler" is a bit confusing. But it feels like I'm several decades too late to complain about it ;)
        • kwertyoowiyop 3 days ago |
          Using “assembler” instead of “assembly” was common enough back in the day that there was no confusion. There were 100x more people writing “assembler” than writing actual “assemblers” so you know, the odds were good.
        • snozolli 3 days ago |
          I've never heard anyone refer to writing assembly as writing assembler

          I used 'assembler' back in high school, when I was learning about the 80x86. I remember because I was 'corrected' by fellow student who had never touched assembler, assembly language, machine code mnemonics, or whatever you want to call it.

          I have no idea where I got the terminology, but I was reading a lot of books and Usenet posts on the subject at the time. I'm a native English speaker, for what it's worth.

          • ndiddy 3 days ago |
            > I used 'assembler' back in high school, when I was learning about the 80x86. I remember because I was 'corrected' by fellow student who had never touched assembler, assembly language, machine code mnemonics, or whatever you want to call it.

            Wow, you got the Hacker News experience 30 years in advance!

    • ryandrake 3 days ago |
      I had the same reaction. I first thought, well it's not that difficult to write an assembler for a simple 8-bit instruction set, but then upon reading the article it looks like it's instead writing programs in assembly language. Totally different.
    • emptybits 3 days ago |
      I agree; I read the headline as meaning a 6502 assembler was written, as opposed to 6502 assembly being written.

      Writing compilers gets difficult, quickly. But writing assemblers is/was common enough for simple architectures and it's quite fun and relatively easy to prove/test for correctness. At least compared to most compilers.

      One of my first gigs out of school involved writing a Z80 assembler because I "needed" nonstandard (Sharp/DMG/8080) instructions to be handled during a codebase port. It was enjoyable! I recommend everyone write an 8-bit assembler at least once!

      Still, TFA is very interesting and I appreciate OP's share. :-)

      • PaulHoule 3 days ago |
        There was the time I wrote a “data-assembler” for the AVR8 because I was packing up rather complicated data structures to represent parts of graphics that appear on a persistence of vision display and how the parts are assembled into images. If you look at any assembler you see there are a lot of facilities for constructing data as well as for constructing code and I took one approach to that problem, outputting C code for an array that the system can read out of the (comparatively large) ROM.
      • spc476 3 days ago |
        I wrote my own 6809 assembler [1] largely just because, and I ended up adding a 6809 emulator to it, so I can run tests during the assembly phase. I'm only aware of one other assembler (a 6502 one) that can do this. It's a fun project.

        [1] https://github.com/spc476/a09

        • PaulHoule 2 days ago |
          I’ve been thinking about how to add tests to assembly code, that looks like a good idea.
    • 0xcde4c3db 3 days ago |
      In my experience, this is a common enough usage variation that I'm not sure how helpful it is to treat it as an error. In particular, "assembler language" seems to have been IBM's preferred phrasing at one point.
    • satiated_grue 3 days ago |
      As someone who's been writing assembly language for decades going back to Univacs, most people used "assembler" as shorthand for "assembly language" or even "assembler language". It's usually quite unambiguous.

      Here are examples of such usage, from 1967 and more recent:

      http://www.bitsavers.org/pdf/ibm/360/asm/C28-6514-5_IBM_Syst...

      https://www.ibm.com/docs/en/zos-basic-skills?topic=zos-assem...

      • pessimizer 3 days ago |
        Seems like they always start with "the assembler language," which I take as "the language of the assembler," and then they sometimes get sloppy after that. I've never heard someone say "assembler language" (or maybe I just tuned it out.)
        • AlotOfReading 3 days ago |
          It's definitely a thing that happens. I believe it comes from the phrase "assembler language" that IBM manuals used instead of "assembly".
    • Dwedit 3 days ago |
      Other mistakes everyone makes: Referring to an instruction as an Opcode.
    • sehugg 3 days ago |
      And if you write an assembler in C#, you could have an assembler in an assembly.
    • tomcam 3 days ago |
      I made a living writing assembler as early as 1986. We used assembler and assembly language interchangeably, even though it’s true that the actual executable software that parses and generates code is called an assembler.
    • radarsat1 2 days ago |
      Imho these kind of pedantic comments detract from discussing the content of the article.
    • unwind 2 days ago |
      Non-native English speakers might also be a contributor to this, for instance in Swedish the words are the same so "assembler" can refer to either the language or the tool.

      As usual in natural language it's pretty clear from context which one is meant. Not sure about other (larger) European languages, it seems it's possible usage in German but it's not the primary case from a quick search.

  • cpldcpu 3 days ago |
    Which LLM is Amazon Q based on?
  • nxobject 3 days ago |
    This raises the question: what information did Amazon Q ingest to be able to write C64 Basic, and from where – OCR'd books and magazine off Google Books? Online tutorials? That would explain whether it would be possible to adapt this workflow to supporting other relatively obscure platforms, with a limited documentation set that's certainly not available online on the internet in easily parsable HTML: e.g. PDP-11 assembly, Turbo Pascal, classic Macintosh/Macintosh Toolbox, etc.

    Who knows, it might be a shot in the arm for retrocomputing enthusiasts.

    • duskwuff 3 days ago |
      > classic Macintosh/Macintosh Toolbox

      This one's probably pretty well covered, actually. All of Apple's Inside Macintosh documentation is available in PDF format, and there's plenty of old programming books and magazines which have been scanned and OCRed.

      • Someone 2 days ago |
        Inside Macintosh has very, very few code examples (the only one I remember is the example program at the start of the phonebook edition)

        Without large code examples, can a LLM write even halfway decent code?

        > there's plenty of old programming books and magazines which have been scanned and OCRed.

        In my memory, the heyday of printing programs in magazines was before the Mac. Macintosh programs were too large to print in a book or magazine, and other methods to distribute code were available (ftp servers, CDs)

        I would think a good LLM for assisting working on the Mac toolbox needs data from ftp sites and CDs.

    • 094459 3 days ago |
      Yeah it lowers that barrier to getting re started. It did for me at least
    • renewedrebecca 3 days ago |
      I don't think I've met a retrocomputing enthusiast yet who has a positive opinion of generative AI.
      • antod 3 days ago |
        Makes sense to me. Part/most of the appeal of coding 6502 or z80 for a retro platform is just how deterministic and predictable they are down to the clock cycle. AI is the opposite.
    • jhbadger 2 days ago |
      I find even local LLMs like Llama can do a fair bit of retrocomputing, from BASIC to 6502 and Z80 assembly language. I doubt very much that they were specifically trained to do this; I think it just comes for free because the broad training these LLMs get from random text taken from the Internet contains this sort of stuff.
  • vardump 3 days ago |

      // Zero page variables
  .const zp_x = $FB
  .const zp_y = $FE
  .const zp_dx = $101
  .const zp_dy = $104
    AI extended zero page, I see… (zp_dx and zp_dy are in 6502 hardcoded stack range, not in zero page at all).
    • sehugg 3 days ago |
      I've noticed that LLMs have a hard time remembering all the constraints of 8-bit programming. Like sometimes it assumes that 6502 registers can have a value above 255, or in C it assumes that ints have 32/64 bits.
    • surfingdino 3 days ago |
      $101? $104? This looks familiar. If you try to train an LLM on series of lottery ticket numbers, say 1-50 and then ask for a set of numbers based on the training data LLMs sometimes will give you numbers like 110 or 101.
    • Dwedit 3 days ago |
      Also, if you have an array living in the zeropage, and you use Zeropage,X or Zeropage,Y instructions to try to access beyond address FF, it will wrap back to 00. Because it's a zeropage instruction that can't go outside the zeropage.
  • PaulHoule 3 days ago |
    Reminds me a lot of BASIC I wrote back in the day, particularly the code for the bouncing sprite.

    Seriously though it makes me think of how hit-or-miss Microsoft Copilot is at writing code (we have a special license to use it at work.)

    For certain things such as writing short bash, CMD.EXE and PowerShell scripts it does great. It writes great list comprehensions in Python. Can convert code defining a set of typed dicts to a set of dataclasses. Can write a SQL query using an obscure (to me) feature and then rewrite it in JooQ.

    But write a CTE expression in JooQ? It doesn't understand how to break the circularity.

    Configure Vite? It will insist on the same wrong answers ceaselessly. On the other hand, if you look at StackOverlow the answer seems to be "you can't get here from there" or "there is this plugin that might help if it worked but it doesn't."

  • 094459 3 days ago |
    Author of the post here. Just reading the comments so apologies for getting some of the terminology wrong. The intention was never to mislead folk , just wanted to share my enthusiasm for emulation and the fact that you could get working code.
    • ewalk153 3 days ago |
      Lovely post. Thanks for sharing.
      • 094459 3 days ago |
        Thank you!
  • russellbeattie 3 days ago |
    Shout out to Ben Eater for enabling me to understand this article. Everything I know about Assembly and the 6502, I learned from his videos.

    https://eater.net/

    • ewalk153 3 days ago |
      Same. After finishing my breadboard computer, I followed along Nand to Tetris: https://www.nand2tetris.org/

      Combined, hardware is finally approachable down to the gate level, even when modern systems add many layers of abstraction.

    • 094459 3 days ago |
      Omg these are amazing. Have not seen these resources before
  • CyberDildonics 3 days ago |
    Where does the future come in to this? This title seems like a stretch.
  • johnea 2 days ago |
    I'm really into retro computing!

    I use my fingers and 9 small rocks...

  • NikkiA a day ago |
    They needed to ask Q to know why (x>255) failed in a poke? I despair.
  • Ambix a day ago |
    I did started learning 6502 assembler back in those days :)

    Recently I have been busy writing the emulator in Golang:

    https://github.com/gotzmann/6502