PCB "sea of gates" (676)

Cluso99Cluso99 Posts: 16,383
edited 2019-10-25 - 08:03:25 in General Discussion
For some time I’ve considered building my own processor from just gates. A week ago I had some time to waste so I messed around with the idea again. Last w/e I put it on a pcb design. The result is a 4”x6” pcb with 676 gates in a 26x26 matrix.

I used the 74LVC1G58 in the 6pin SOT363 footprint which is ~2x2@.65mm. This is a configurable gate as a 2 input NAND/OR/XOR/INVERT or an AND/NOR with one input inverted. Of course, the footprint also permits the use of 74LVC1G98 (NAND/NOR/2:1 MUX/INVERT or NAND/NOR/AND/OR with one input inverted), or 74LVC1G11 (3 input AND) or any SOT363/SC70 with centre power pins.

At 3V3 operation the gate delay is 6.3ns max.

Wiring is done using kynar wire. Each gate input has a pad with 0.7mm hole and the gate output pad has a 0.5mm?? hole.

These boards could be stacked. I’m thinking a Z80 would probably need some 10 boards stacked, plus a special board for the registers made with 74LVC646 which would probably have a 128KB SRAM too, and maybe some I/O.


  • jmgjmg Posts: 14,418
    .. or.. you could just use a P2 to emulate all those manually connected gates ? ;)
  • Yeah, but that’s less fun!
  • ercoerco Posts: 19,738
    edited 2019-10-24 - 17:06:01
    Quite a project!

    Dave Bowman said that in 2001 and again in 2010:

    "My God, it's full of gates!"

    Also heard often at Bill & Melinda's family reunions...

    I got more.
  • Cluso99,

    With the miles of wire the electrons will now have to navigate I think you will be lucky if you even get within a few percent of that speed.

    Oh, and it will make a nice space heater in the winter.
  • I’ve been playing with the register design (Z80) in my spare minutes over recent days. The 74LVC646 design is taking shape. This IC can perform 2 8-bit registers, so for example the A and A’ register pair. It can also serve as a buffer/isolator ie a 74LVC240 replacement. I like to use the same IC in as many places as possible as it keeps the BOM simpler :)

    The Z80 register section seems to use ~1792 transistors just for the registers. The whole Z80 uses ~8500 transistors so this is around 21%. Of speciation note is each register bit uses 4 transistors and 2 resistors which includes the bus pass transistors. These days a CMOS SRAM bit uses 6 transistors. The Z80 used SRAM registers even tho the cpu was not a static design (ie requires continuous clocking).
  • @Cluso99 This project is utterly sick, wrong, and clearly the product of a deranged mind. You should seek professional help immediately.

    Translate: I TOTALLY LOVE it! Please post update and pictures! And I’m not joking when I say I’d buy the inevitable kit from you just so I could build it and drive a few local friends crazy.

    Write when you get work (or if you need help with a CP/M port. Hehehe)
  • @JRoak Yeah, tell me about it ;)

    I have 2 hours on 2 mornings where I look after the grandkids before school, and before I go off to work. This is when I get time to just dream and lately I've been delving deeper into the design of the Z80. I did designs using the Z80 back in the early 80's before moving onto the Z8 (Z8681) from Zilog, but I'v designed lots of products with many different micros from the mid 70's onwards.

    Anyway, I've been delving into Ken Shirriff's blog on just how the Z80 was built. It's really fascinating stuff looking at the die.
  • Cluso99,

    What do you plan on doing with your Z80 contraption?
  • Genetix wrote: »

    What do you plan on doing with your Z80 contraption?
    Nothing spectacular. Just because I can really.
  • “Just because I can, really.”

    Driving force behind everything I do in this field!
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