Using an 80186
Support for operating an Intel 80186 is in development.
When building the cpu_server sketch for an 80186, make sure that you set
#define CPU_186 1
or the sketch will not function. The 80186 has a different reset procedure. It is possible this could be auto-detected, but for now you'll need the define.
The recommended model to use is the Intel 80L186EB. This is a 3V variant of the 186 which is convenient as it allows direct connection to the Arduino DUE's GPIO lines with no level shifting.
This CPU was available in three speed bins, any of which are adequate: 80L186EB16, 80L186EB13, 80L186EB8. New old stock is still available but often minimum order quantities apply. They sometimes show up on eBay.
Warning
Searches for "80L186EB" sometimes return results for "80C186EB". The 80C186EB was a 5V part, I have not tested it to see if it will function under 3V operation. If you try it, let me know.
No PCB HAT has been designed for the 80186. Instead, you should use a TQFP breakout board. You will need to use a 3V version of the 80186 as we will be connecting it directly to the Arudino DUE's GPIO.
Make connections to the Arduino DUE's headers as follows:
Successfully soldering a TQFP requires good soldering skills. Solder paste and a hot-air station is recommended, but the part can be successfully hand-soldered with solder wire. I recommend browsing Youtube for "SMC soldering tutorial" or some other relevant search until you feel confident.
Positioning the chip on the board can be made easier by attaching the chip to a piece of Kapton tape, lifting one edge off the board at a time to adjust the position of the chip in small increments via the leverage provided by the tape.
Be sure to carefully inspect the CPU after soldering to ensure no pins have a solder bridge. In the worst case scenario you bridge 3V to GND and destroy the chip immediately. A multimeter with a continuity tester should be employed to check there is no connection between the 3V and GND pads.