The Neo6502 Is A Credit-Card Sized Retro Computer

The venerable MOS Technology 6502 turned up in all kinds of computers and other digital equipment over the years. Typically, it was clocked fairly slow and had limited resources, but that was just how things used to be. Today, the 6502 can run at an altogether quicker pace, and the Neo6502 was the board built to take it there.

The Neo6502 from [Olimex] is a credit-card sized retro computer built around the W65C02. If you’re unfamiliar with that chip, it’s essentially a 6502 that can go fast. How fast? It can be readily overclocked to a blazing 16 MHz, if you’re so inclined!

Unlike some 6502 retro builds, the Neo6502 doesn’t live so firmly in the past. It’s outfitted with an HDMI video interface to make it easy to hook up to modern monitors, so you needn’t fuss around with old displays. Similarly, it has a USB host port to accept input from a keyboard, and audio out via a 3.5 mm jack. There’s also a tiny PCB-mount speaker, as well as I2C, SPI, and UART interfaces. Finally, there’s 2 MB of flash onboard, and a 40-pin connector hosting all the 6502 signals that you know and love. Which is all of them. Much of this lavish equipment comes courtesy of an RP2040 microcontroller onboard that handles all the bits and bobs that aren’t fit for the CPU itself.

It’s still a new project, with things like a BASIC interpreter currently in development and boards not yet openly available.  But, if you’ve always wanted to play with a hotshot 6502, this could be the board for you. Try out the emulator and see how you go.

53 thoughts on “The Neo6502 Is A Credit-Card Sized Retro Computer

    1. Yes, for a processor to emulate the I/O functions for another processor, it generally needs to be faster than the target system. But, of course, for the optimal retro experience we want to run 6502 code on real 6502 silicon!

      1. That’s not true though. The 6502 does not contain some analogue magic that’s hard to replicate.. Cycle-accurate emulation of an entire system can be a challenge, but the 6502 is not even in the realm of being the difficult part of that.

        It’s silly to have a more powerful processor serve as an IO adapter for a less powerful one, even for the “true retro experience”, having a layer of more powerful hardware between you and your program makes it in effect the same thing as emulation.

      2. This is because there are flaws in the 6502 that can cause a person expecting it to work perfectly to go insane. The 65C02 found in AppleIIc fixed those and some undocumented opcodes that used to be a boon to programmers became either unusable, or new official opcodes.

        The Apple-II GS had Western Design Center’s new WDC65C816 which increased the flat memory space to 16 megabytes, and allowed either 8 or 16 bit data instructions while maintaining near hardware compatibily with the 65C02, 6502, and 6502C. I once dropped a 65C816 in a socket on an Atari and only needed one externally attached TTL gate to make it run without imcreasing the memory space. That would take a bit more TTL gate to do the buffering and lathching interface to access the highest 8 address bits.

        Lotharek Industries makes adapter boards that drop into those machines and give you all that and more.

        They also have a VLSI FPGA that emulates various computers like the Amiga, PC, AtariST, Commodore64/128, Timex Sinclair Lewis Carrol Channing, Atari 8 bits, etc.

        1. The NMOS 6502 is FLAWLESS ;-)

          TBH, I’m leaning towards the fact that the ‘C02 isn’t even 100% compatible with the original(you couldn’t even be sure one brand of ‘C02 had the same instruction set as the other) and by the time it came out the world had already moved on.

          I can implement a 6502 with many new features on an FPGA that’ll run faster than the wdc65c02… Won’t really make it a “better 6502” though.

          Original, emulated or 1990’s CMOS, to each his own :)

  1. I’m not complaining about HDMI but I feel VGA or even S-Video might’ve been a bit more… topical without being too “rooted in the past” since both are easily converted and HDMI isn’t that much smaller. If size was a factor than micro HDMI would’ve made more sense.
    I appreciate the audio jack; does it also have audio input for – say – emulating a casette?

    1. Modern displays and TVs don’t seem to have VGA or S-Video. So if that’s what people are using it for, it doesn’t seem like a benefit to add digital to analog conversion to the board, just to use an adapter for analog to digital, and end up with HDMI anyway with some quality loss.

      HDMI to VGA converters seem more common and readily available anyway. Those are commonly used in places that still have mounted projectors wired with VGA even though no one’s laptops has VGA ports anymore.

      1. Again; not complaining about the inclusion of HDMI. This is just one of those instances in which I actually do feel that mini or microhdmi would’ve been more… suited.

        That said, it’s a bit better to convert analog to digital rather than vice-versa, tbh.

      2. “HDMI to VGA converters seem more common and readily available anyway.”

        At the moment, yes.

        But let’s think of the future. Composite and VGA are easily being understood, can be displayed on a bare oscilloscope, even.

        HDMI will be forgotten in 20 years, by contrast, it will be meaningless. Like DVI or Display Port.

        And that’s what people don’t seem to ever understand. 😔

        1. I too appreciate the simplicity of analog video, but you’re declaring the death of DVI and DisplayPort rather soon. DisplayPort is a regularly updated standard in common use (just for computer monitors, not TVs), and DVI is electrically backwards-and-forwards-compatible with HDMI. (not counting DVI-A, which is, of course, just VGA in a funny connector.)

      3. Even if a TV has VGA, I found that it’s totally useless. As they do “bare minimum so we can tick the box”. So it stretches 1024×786 to whatever resolution the TV really is, and don’t accept any other resolution.

      1. > I do not see point to emulate cassete input as no one keep cassete and tapes anymore.

        While you’re correct that tape isn’t popular anymore, folks do have sound files of old cassettes and usually use something such as an MP3 player to play these sound files back to the computer when they want to load them.

        Folks usually don’t want to butcher their piece of computing antiquity, so playing audio back remains the main method of loading data for those with ZX81s, C64s, BBC Micros, etc.. (Although I had a 5 1/4″ disc drive on my BBC Model B, some versions of software were only released on tape.)

        Anyway, I love 6502 and happy to see this project. Would be great if it could be configured to be more of BBC Micro than C64-ish.

        1. Honestly, I think his basic argument is invalid because it focuses too much on specific media.

          The ability to encode digital data as analog audio (and recover that data from the audio) is far more versatile and easier to recreate than a much more complicated storage medium.

          And because sound and music will likely never become irrelevant…

      2. > no one keep cassete and tapes anymore

        I’d argue that this logic invalidates the entire project. In the context of what’s going on here, it’s audience is more than prepared for — if not excited by — that feature’s inclusion.

        1. Cassette converting programs exist for various cassette file formats. Kansas City Standard FSK and various other formats. If you still have cassettes that need to be converted then be sure to use good audio cassette deck with the appropriate EQ and Bias settings to record them as a mono (or stereo for some mixed digital analog Atari programs) to a WAV file or other lossless format. Its possoble to recover stretched or somewhat damaged tapes for old computers, CNC machines, Typesetters, Wordprocessors, Etc even Sewing and Embroidery Machines using Hilbert-Huang or FFT. The low data rate used by casette tapes of typically 300 bps helps recovery and conversion a lot.

          Your data is there, and can become accessible again.

    2. IMO VGA isn’t different enough in picture quality for what they’re doing to be worth it except as some kind of purism thing. As for S-video, making a modern board with video ports that modern monitors literally don’t have kinda defeats the purpose. Yeah you can convert it, but the percentage of people who would actually use S-video probably rounds to 0,so what’s the point?

      1. VGA allows all kinds of timings, it has no copy protection, has no patent issues. VGA means freedom. It’s also perfectly fine up until 1080p, at least. The actual maximum resolution/refresh of VGA depends on the RAMDACs used (respectively, their speed in MHz).

    3. Yah. I’ve had that same argument here SOOO many times.

      The common answer is always that HDMI is everywhere and people can’t find VGA anymore. I don’t get that.

      Personally.. the Livingroom TV is NOT where I do hobbyist stuff normally. Neither is the bedroom TV. Those are shared with the household and the wife respectively. Hobbyist stuff gets relegated to my own space. This is fine but I for one am NOT going to the local box store and picking up a brand new gazillion-dollar television for hobbyist stuff.

      Instead hobbyist stuff gets done on old computer monitors saved from an upgrade, scavenged from an office closet or bought at the local thrift shop. $20 would be on the epensive side. And it’s pretty damn rare that any of that stuff does HDMI yet! Maybe in about 2035 or so. I suppose hobbyist boards will all be outputting something else by then though.

      As best as I can tell, HaD authors, most commenters and the people designing boards all live in tiny big city apartments where space for a dedicated hobby monitor is at a premium but money to throw on the latest TV is not.

      Oh well.. Just do yourself a favor, watch Amazon and buy a bunch of HDMI to VGA adapters the next time you see a good deal.

      1. In this case they use HDMI instead of DVI since it is a smaller port and it was some time ago that I saw a VGA only screen.
        Also, as far as I know the Pico does not do audio over HDMI.
        Also Also, the HDMI uses less pins than VGA, usually, does on the Pico. I would love to see 1, 3 and 6 bit VGA mode but it seems not be any big demand for it.

    4. “I’m not complaining about HDMI but I feel VGA or even S-Video might’ve been a bit more… topical”

      But even authentic period retro hardware enthusiasts are putting HDMI conversion hardware in them (which, amusingly to me, use modern processors vastly more powerful that the entire machine in which they serve only to do that video conversion). And in forums for cheap, retro SBCs, people are constantly complaining about no HDMI output. Of course, cheap VGA to HDMI converters are available, but it’s nice to have that built in.

      1. I’m not sure why this would amuse you? Each part of a system is designed to do its job as best as it’s capable of. For running retro 6502 code, there is nothing better than running the code on actual 6502 silicon! Likewise, for converting analog video to provide the best picture on a modern HDMI input digital display, you want a device that is capable of doing the best job at this task. I don’t see why this would amuse anyone?

  2. I’m working on a Ben Eater 6502, nearly to the point that I can run WOZMON on it. (That is an amazing 256 bytes of code!) I’m definitely going to be keeping an eye on this. It would make a nice addition to the breadboard, and hopefully a custom PCB version eventually.

  3. I think it’s cool for special applications, if there are any for 6502.
    Like, installing in a model (r/c plane, balloon, boat)..
    Or running CP/M-65:

    But in general, I don’t like miniaturization. I prefer functionality. Big, modular and expandable systems are cool, thus. With big connectors that have screws or clamps (DB-25 or Centronics). Something professional, long-lived.
    An 6502 or Z80 system makes sense as a controller in an industrial circuit.
    For that purpose, Euro Card Bus (ECB), S100 or any other modular format is recommended.
    These form factors are nice for 19″ rack chassis, too.

    1. “Looking forward to seeing where this goes.”

      Funny, I was reading “looking forward to see where this geos.” 😆
      As in “GEOS”, the GUI for C64 (another 6502 or 6510 system).

  4. What the article doesn’t mention doesn’t mention is that the board only costs €30 which is a complete bargain compared to many offerings that go up to $500 for a similar offering (albeit with built in peripherals). I’ve had the dev version of the Neo6502 for a while now and it’s been really nice to play with. The production version of the Neo6502 will be available soon and at this price it’s a no-brainer!

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