“Zero Overhead” Z80 Computer Focuses On Performance


There’s something quite satisfying about building your own computer. Nowadays, constructing your own desktop PC is relatively easy, so if you really want to get your hands dirty, you have to take a step back in time and give some vintage hardware a spin.

[YT2095] has spent a good portion of the last two months building a computer based on the classic Z80 CPU. His machine, called “Z Eighty Development” or “ZED” for short is an amazing build, and most definitely a labor of love. He has put an estimated 700+ hours into this machine and it’s a beaut! When closed, the machine is pretty unassuming, but once he folds down the keypad, you can see that all of his time has been put to good use.

Most of the board’s components are connected together via wire wrap, including the large 48k memory card he built, as you can see from the link above. The wide array of add on cards all work together to accomplish his goal of “zero overhead” – freeing up the Z80 from having to do any unnecessary processing, such as I/O, etc.

It’s quite an impressive build, and ranks up there with some of the best Z80 based computers we have seen through the years.

33 thoughts on ““Zero Overhead” Z80 Computer Focuses On Performance

  1. I too appreciate the elegance of wire wrapping on the component side using male headers. Wondering if it is just plain old perfboard with the headers glued down or if their are solder pads on the backside to secure the headers & sockets.

  2. Woops! If I’d read more carefully his method is described as a “soldering/wire-wrap hybrid that Top wires circuit”. Not only would this way be cheaper than traditional wire wrap sockets, but much easier than flipping and connecting on the backside which is a pain and error prone.

  3. @Joe :Come on, the Crysis thing is a classic. I lol’ed. But seriously, this is pretty awesome. I love the z80, and the zero overhead is a really amazing feature. Maybe it would run Crysis?

  4. I wonder if he’s ever going to make an mp3 addon card. Or wire one of these up to it: http://excamera.com/sphinx/gameduino/

    Yeah, it would be a little pointless to have a board with a fpga that you could implement the entire computer on running just the graphics. It’d still be cool. And he wants zero overhead and to offload as much as possible from the Z80 cpu….

  5. Holy hell. Forget building something ‘half as good’ — I wish I could just build one of those freakin boards he’s using! Or even half of one! But then, guess I’ve always been more of a software guy than hardware. But hell, this is….wow.

  6. Hey YT… Instead of using lookup tables to create your sine waves.. you should dig up some old C=64s and rip out a couple SID sound chips. Hook yourself up with some multi-voice, polyphonic “retro sound”. :)


  7. @JD,

    The 700 hour figure was an estimate on our part, though it should be *fairly* accurate. He says that it was the product of “2 months work, often 12 hours a day”. That comes to about 700 hours, give or take a few.

    If it was less than 700 hours, it makes it all the more impressive, imho. That’s a hell of a lot of work no matter how you cut it.

  8. This guy needs to start a PC company to compete with big brands like Dell and Toshiba. If he can redesign a high quality PC with Zero Overhead nothing before could compare to it.

  9. I wouldn’t mind to put something like this together. Granted that I’m no EE, but I don’t think it would be too hard. Just wire the pins to the right ones.

    Just all those wires… GOD! Blow out a few chips. I would be like fuck it. It’s time to learn some CAD software!

  10. “bandwidth exceeded”, The ugly on relying on free, and/or the least expensive paid web services shows it’s ugly head. Hard telling when the freebanders page/post will be available for viewing. Instructables may not be that bad after all, I never have read about a complaint with a bandwidth exceeded message in regards to a project hosted there. Perhaps Google Docs would be an alternative?

    smoketester says; Woops! If I’d read more carefully his method is described as a “soldering/wire-wrap hybrid that Top wires circuit”.

    Thats sounds like a fancy name for old fashioned point to point wiring atop an actual wood bread board. Again I can’t see any images.

  11. damn that`s a pity about the photobucket thingy wanting to extort money from me!
    does anyone know a place I can host these pictures again for free?
    they`re still on my Camera so it shouldn`t be too hard to transfer somewhere else (I hope).
    sorry about that each!

  12. nevermind, I paid their ransom, and the pics should be back up again for a month once it propogates through the servers and rubbish.
    to answer a question about the method I used on the boards, they Are soldered into Vero board, so in effect I decide the IC holders placements according to real estate on the board and allow for 2 holes worth of space either side of the chip socket to run the male header strips, these are all soldered in (headers and sockets) and then the tracks cut to isolate them from the rest of the board, they are them wire-wrapped together in a lovely spaghetti mess, that`s for some reason perfectly stable at 8MHz (I seriously did expect some noise and instability).
    quite a few of these cards were wired up in bed! I wasn`t feeling very well during most of the construction, so I would do all the soldering in the morning, and then spend the afternoon in bed wire-wrapping, designing for the next day, and then reading Z80 machine code manuals before bed time.
    so probably closer to 16 hours a day each day with Something ZED related, but closer to 12 on the actual Build side of things.
    some stats, there are currently 62 ICs in use on there, 600 feet of wire-wrap wire used, roughly 2000 wire wrap joints and well over double that for solder joins, it pulls exactly 1.64 Amps, all at 5 volts except for the 12 fan to keep the regulators cool.
    and if I got bored with Z80, I could easily make and drop in a 8080 cpu card or any other 8 bit CPU and use that just as easily, although it would mean learning more machine code! so I probably wont be doing that :)

  13. Quite impressive! I like the wiring job and technique too.

    The use of MCUs to offload tasks seems a bit of a “cheat”, not really true to the retro spirit of the rest of the project; since each MCU can be almost as powerful as the main CPU and much of the other hardware! Regardless, it’s an interesting fusion of old and new. A Propeller would probably make an excellent co-processor too, possibly able to do everything all three of those MCUs can and then some.

  14. Yes, I can fully appreciate How this may seem like a cheat using embedded hardware for external support and how that may not seem “fitting” with a purely (and totally incidental) Retro-look.
    the whole “Retro” thing was not not my aim, it just turned out that way by chance and convenience.
    the idea was that I`m just a Hardware hacker, and so I`m using things I CAN do to create a platform that will expose the Z80 as purely a concept, thereby allowing me a greater intimacy with its core.
    from This standpoint I can Learn and Develop More hardware, and Join the 2 together, as a stepping stone towards Other processors and machines.
    I`m Old School, so an FPGA or CPLD etc… means little more than an utter nightmare of over-bloated arbitrary s/ware manipulation excersize leading to nothing more than frustration!
    I`ll take a handfull of 74 or 4000 series chips and a soldering iron over billy gates`s garbage ANYDAY!
    sorry to sound bitter, but you have to work with what you have, and more importantly what you Know!

    I have no objection to Learning stuff, I DO object to learning stuff that will be redundant next week and subject to the whim of someone else.

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