POLON 7880

8-bit microcomputer, based on the Polish CPU, manufactured thirty years ago.

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Some time ago I bought a few pieces of the MCY7880 - a CPU manufactured in Poland in 1980's, by CEMI corporation, which no longer exists - it fell victim of the economic transformation of early 1990s. The device itself was a clone of an Intel 8080 chip. It is interesting artifact, a witness to history of both: my country and computer technology.
Since it came to me I was sure, it won't end up merely as a decoration. I wanted to see it running some code! So my project began...

The main idea behind this this project is to build fully functional 8-bit computer, using as many Polish ICs from the 1980s as possible. Of course I had to draw the line somewhere - I decided not to use small, hard to get and difficult to use DRAM chips manufactured by CEMI. I used more modern CMOS SRAM chips instead.

The project is highly experimental in nature - different from anything I've done before, so I decided to mount in using universal PCB and a wire wrapping wire. A lot of kynar wire. It was a detour from my usual way of designing and etching PCBs. To my great surprise, I made only a couple of mistakes while wiring this thing and debugging wasn't difficult.

Just like the original 8080, MCY7880 requites three supply voltages: 5V, -5V and 12V. First one is delivered directly by the main power supply. The latter are generated by the charge pump and boost converter.

At this point computer is running TinyBASIC, using serial terminal as an I/O. it is still an ongoing project. I plan to build few additional boards containing CRT screen controller, keyboard interface and maybe even use a CF card to boot CP/M and run Zork.

  • 1 × MCY7880 Polish 8-bit CPU, Polish clone of Intel 8080
  • 1 × MCY8255 GPIO/parallel port. Polish clone of 8255 chip.
  • 1 × UCY74S428 Bus controller, Polish clone of an 8228 chip
  • 1 × UCY74S424 Clock signal generator, Polish clone of 8224 chip
  • 2 × D43256C 32kB Static RAM

View all 18 components

  • It has it own case now

    Marek Więcek07/23/2022 at 18:23 0 comments

    Computer finally got it own metal case. I also used that opportunity to upgrade power supply. Now POLON is powered directly from 230V mains power.

  • It supports TV now!

    Marek Więcek05/20/2021 at 12:44 0 comments

    Some time ago I was able to make some further developments.

    At this point computer is able to supporty standard PS/2 keyboard and print text on TV screen. Due to lack of time I wasn't able to make any further developments in recent months, but soon I will try to write some assembly code, implementing simple terminal screen.

  • Significant update

    Marek Więcek11/11/2019 at 11:03 0 comments

    Project grows. Recently I added second board, containing some chips:

    • M6242B real time clock
    • 8242 AT keyboard controller
    • 8259 interrupt controller
    • TMS9929 video chip with SRAM memory

    There is also a connector for CF card module.

    After testing added components under TinyBasic my plan is to port and run CP/M on this small computer.

View all 3 project logs

Enjoy this project?



teraz wrote 05/09/2022 at 20:58 point


  Are you sure? yes | no

Ken Yap wrote 01/28/2019 at 14:28 point

Cool, I like retro. Some interesting comments here:

  Are you sure? yes | no

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