A freeformed computer based on an Intel 80186 with 16 KB eprom, 1 MB ram and a serial port.

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Having done a few freeformed designs (among others the old Lethal Nixie Cube, the WireZ80, and the Blinken Grid) it's now time for something slightly more complex. I have an old 80186 CPU that I bought a while back just because it was so pretty and I realized that it would be perfect to use in a freeformed project.

Being a Intel X86 compatible CPU with a lot of the required peripherals, like the special clock driver, dma, interrupt controller and address decoder, already built into the chip the number of ICs I needed to add is reduced a lot.

Unfortunately it's a 80186 with has a 16 bit external data bus, in contrast to the 80188 that is 8 bit external, so I need to add two eprom and two ram chips to get up to the required databus width.

If I write a custom BIOS for this I might even be able to boot and use some early MS-DOS even if I don't have neither a video card nor a disk drive connected to it.

Log entries

1. Framing the CPU
2. VCC and Crystal

  • VCC and crystal

    matseng02/08/2019 at 12:34 0 comments

    Since I have GND in the outer bigger frame I made a small frame for VCC and hooked it up to the two VCC pins on the CPU. I also added two 100n caps between VCC and GND.

    I discovered that I don't have any thru-hole caps in the pF range so I had to improvise a bit by soldering two SMD caps between the pins of the crystal and then hook up a ground wire between the caps.

    After adding some 10K pull-ups to the inputs of the CPU that must be held high while running I could got a nice waveform at the clkout pin and a lot of randomly-looking toggling at the combined address/data-bus pins.

    So it seems that the CPU is not completely dead at least :-)

  • Framing the CPU

    matseng02/08/2019 at 11:26 0 comments

    I want to have the CPU prominently visible in the design so I used the technique with having high value resistors for mechanical support of the parts.

    To get everything neatly aligned and even I made a template (in Eagle) and printed it to aid me during soldering and bending. 

     I was a bit afraid that the thin gold layer that are connections on the ceramic chip would break off when I bend the resistors, but apparently they are more robust than I expected or I was just lucky because when I was done everything was still in one piece.

    I really would like to keep the "rays" outside of the frame, but I know they will end up being bent and crooked in all directions before I'm done soldering up all of the parts in this project so I cut them off. ;-(.  

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Dan Maloney wrote 02/08/2019 at 16:02 point

Wow, I love it! You don't see much love for the 80186, and this is a great way to display it while putting it to work. Keep us posted!

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