4 ms·

The bottom photo shows an ATmega328P. So this is just a software emulation of an Apple I? What’s the point?

• greatjack613 7y ago
  was wondering the same. Just run an emulator on your raspberry pi, no need for a single use kit
• michaelmior 7y ago
  Even if it's an emulated Apple I, the kit looks like fun :)
  • sergpanarin 7y ago
    Thanks!) But it’s not emulated - it uses microcontrollers for keyboard&video and original CPU 6502 with ROM/RAM to do the work. Original Steve Wozniak’s code is on ROM. ROM chip is bigger then in the original and it’s possible to load BASIC interpreter or other programs and run them from ROM
• jhbadger 7y ago
  I think it is just there for generating the video signal. This sort of thing is common. The earlier (solder-based) Briel Replica I Apple I clone used a Propeller chip for that. But it still had a 6502 for the actual computing, and I imagine this does too.
  • erik 7y ago
    A lot of modern hobby computer projects use a FPGA, micro-controller, or dedicated modern CPU to bit-bang the video signal. How did the original 8-bit computers do it? Did they have access to chips that are no longer produced?
    • randrews 7y ago
      Exactly. :)
    • jacobush 7y ago
      Yes, they had.
    • duskwuff 7y ago
      The Apple I and Apple II both used discrete logic to generate a composite video output. The Apple I used a couple of unusual Signetics parts (2504, 2513, 2519) and a character generator ROM to implement a text-only "video terminal" with a UART-like interface; the Apple II used a more complex system built around the system's DRAM refresh which allowed for graphical output. None of this required any truly unique parts (although the Signetics parts used in the Apple I are hard to find nowadays), but most hobbyists prefer something more modern than composite video. :)
      • simcop2387 7y ago
        It's also a problem using discrete components for noise and EMC compliance, you need a shielding because you have a lot more higher frequency traces compared to otherwise. It's still possible to do without too much trouble but compared to doing most of it in a single devices there's just very little point in spending that much work most of the time.
        • duskwuff 7y ago
          EMC compliance isn't really a concern until you're building a consumer product. A breadboard kit… nah. :) Noise is a real issue -- but the main concern there is the CPU. Video generation isn't unusually noisy.
          • wizardforhire 7y ago
            “EMC compliance isn’t really a concern”... Unless you’re this guy https://hackaday.com/2019/05/15/the-great-ohio-key-fob-mystery-or-honey-i-jammed-the-neighborhood/ https://hackaday.com/2019/05/15/the-great-ohio-key-fob-myste... But seriously, you’re totally right.
    • LIV2 7y ago
      Most used the 6845 CRTC or compatible but the Apple 1 used discrete logic & shift registers instead of CRTC & RAM from my understanding I don't think the particular shift registers etc are still available but it is still possible to do it with discrete logic these days I guess different projects have different focus and some probably don't care too much how they get video as long as it works. I've built discrete and CPLD based video circuits for my own 6502 project which is fun but took months to get working perfectly
    • derefr 7y ago
      Enlightenment may come from looking at an IBM-PC MDA (Monochrome Display Adapter) board: http://www.minuszerodegrees.net/5150_5160/cards/ibm_mda.jpg http://www.minuszerodegrees.net/5150_5160/cards/ibm_mda.jpg ...or a VT100 main-board: http://i.imgur.com/Xae4be6.png http://i.imgur.com/Xae4be6.png 80% of these boards are "the graphics part." Dozens of chips! This is what the sibling commenters mean when they're saying that the video signal is "discrete logic" (as opposed to integrated logic.) It'd be a bit of an ask to have a hobbyist build one of those themselves (adding an 800% complexity increase to what is otherwise a very approachable hobby project.)
      • tyingq 7y ago
        Well, and an exact replica would output composite video, which wouldn't work with anything most people already have.
    • ChuckMcM 7y ago
      http://www.swtpc.com/mholley/RadioElectronics/TV_Typewriter.htm http://www.swtpc.com/mholley/RadioElectronics/TV_Typewriter.... was one of my favorites (the TV Typewriter) Seriously though, as amusing as they are, and as much programming as I did on a 16 line by 64 character "terminal" screen, I really could never go back to that. For grins I set up an xterm that way just to experience it and yeah, it still hurts. A lot. Even the 80 character by 25 line experience (although tolerable for many things) feels so very cramped these days.
  • phaedrus 7y ago
    I built a 6502 "laptop" (a 6502 SBC and LCD stuffed in a toy laptop case). I used a Propeller chip to generate a video signal, as well as to load a program into RAM and generate bus control signals. The 6502 was directly connected to all of the RAM address and data lines, but I could also interpose different values on the database. Another Propeller enthusiast made a pretty good write-up here: http://dangerousprototypes.com/blog/2012/02/22/prop-6502-propeller-laptop/ http://dangerousprototypes.com/blog/2012/02/22/prop-6502-pro...
  • sergpanarin 7y ago
    Yep, I use ATmega just as video and keyboard controllers. All real work is done by 6502 - it communicates with memory and keyboard and video controllers. Just as in the original Apple I
• spongeb00b 7y ago
  It might also be reading the PS/2 keyboard input.