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I was thinking of doing the same thing with my son (breadboarding the Nibbler). He has built a virtual computer with nandgame.com but asked me if he could build

I was thinking of doing the same thing with my son (breadboarding the Nibbler). He has built a virtual computer with nandgame.com but asked me if he could build a real one. The nand game computer is 16-bit and would be a nightmare to build from TTL, but the Nibbler looks doable. This would be my largest breadboarding project by far, though, and I would appreciate any hints you could give me, especially regarding how to test the circuit while building it.

omgtehlion 4y ago
The only way is to build it piecewise, start with generator, clock and PC, then add microcode and code roms. And you will _need_ a chip programmer, something like TL866, this thing can also test simple chips. And a cheap logic analyzer will be helpful. DSLogic is very cool and has 16 lines, but anything cheap from aliexpress will also do fine.
- apricot 4y ago
  Thanks. Do you think the Nibbler would be compatible with Ben Eater's 555-based clock? I think it would be instructive to run it at slow speeds and use LEDs to see how the signals propagate. What would you say was the hardest part of building the computer? How many breadboards did you end up using?
  - omgtehlion 4y ago
    Yes it would. I actually started it with the circuit. It would be somewhat frivolous to call it “Ben Eater's”, as it is a circuit recommended in 555’s datasheet ;) You should put a couple of inverters after the 555 timer to make signal fronts sharper. I recommend 74als series (older, bjt, easier to work with), or 74hct (more modern, mosfet-based, ttl-compatible). We even tried some 74act parts, but these are not designed for breadboards ;) Though Ben Eater’s work is overall great and very instructive. You should follow his recommendations on breadboarding (board models, wires and stuff), they are stellar. The hardest part, as usual in electronics, is contact quality, be careful diligent. For Nibbler we used around 5-6 breadboards. P.S.: it was hard to source ALU. I scoured ebay for weeks and got some for exorbitant price + shipping. Then I found one factory in Belarus that still makes 74als181 (кр1533ип3 in cyrillic) chips in narrow dip packaging. I ordered a small box of these ;) It was cheaper than a single 74hc chip from eBay.

omgtehlion 4y ago

The only way is to build it piecewise, start with generator, clock and PC, then add microcode and code roms. And you will _need_ a chip programmer, something like TL866, this thing can also test simple chips. And a cheap logic analyzer will be helpful. DSLogic is very cool and has 16 lines, but anything cheap from aliexpress will also do fine.

apricot 4y ago
Thanks. Do you think the Nibbler would be compatible with Ben Eater's 555-based clock? I think it would be instructive to run it at slow speeds and use LEDs to see how the signals propagate. What would you say was the hardest part of building the computer? How many breadboards did you end up using?
- omgtehlion 4y ago
  Yes it would. I actually started it with the circuit. It would be somewhat frivolous to call it “Ben Eater's”, as it is a circuit recommended in 555’s datasheet ;) You should put a couple of inverters after the 555 timer to make signal fronts sharper. I recommend 74als series (older, bjt, easier to work with), or 74hct (more modern, mosfet-based, ttl-compatible). We even tried some 74act parts, but these are not designed for breadboards ;) Though Ben Eater’s work is overall great and very instructive. You should follow his recommendations on breadboarding (board models, wires and stuff), they are stellar. The hardest part, as usual in electronics, is contact quality, be careful diligent. For Nibbler we used around 5-6 breadboards. P.S.: it was hard to source ALU. I scoured ebay for weeks and got some for exorbitant price + shipping. Then I found one factory in Belarus that still makes 74als181 (кр1533ип3 in cyrillic) chips in narrow dip packaging. I ordered a small box of these ;) It was cheaper than a single 74hc chip from eBay.