At the time of writing this line I'm 8 month in the project so I'll try to start from the beginning and explain everything that I did since the begining as a recap.

Sorry in advance for my questionable english, it's not my first language.

Febuary 2023

After a year without working on a retro project I decided to start a new project with a intel 80286 that I had found in a parts bin at my workplace. First thing was to read on the subject then I had come across rehsd 80286 project on Youtube (Playlist here) that inspired me to realy start working on it.

Here's the ressources that I had read up to this point :

• Harris 80c286 Datasheet
• Intel 80286 Programmer's Reference Manual
• rehsd - 80286 Build : Youtube playlist and website
• Saldor - 16-bit Intel x86 breadboard computer : Youtube playlist

March to May 2023

My wife and I got our first baby in March so I did not worked much on my retro projects during 2-3 months. Nontheless I had the time to work on my first breakout board for my 80286 CPU and learn how to control the CPU.

I builded a clock circuit with a 555 timer and a variable resistor to help me debug the CPU (the vertical board on the photo).

At that point I began to realize that I needed to order some ICs to help me generate some control signals for the CPU. So I ordered the following ICs :

• 80284 - Clock driver
• 80288 - Bus Controller
• 74HCT245 - for the Data Bus transcivers
• 74HCT573 - for the Address Bus transcivers

June 2023

In my last Z80 I ordered some Altera Max CPLD but after thinkering for a wihile I realized that I had no idea how to program or use them so I put them away. Now I think is time to give them another chance to help me with the glue logic for my 80286. After reading around, I'd put togheter a CPLD programmer on a protoboard for my Altera Max and bought a USB Blaster to connect and program the CPLD via the JTAG header at the botom-right of the board :

After a week of debuging the connections and learning the Quartus software, I was able to upload my first logic to the CPLD.

Now I that I had a working CPU and CPLD breakout boards, I decided to produce some PCBs to cleanly build on a Breadboard :

80286 CPU Breakout board :

CPLD Breakout board :

July 2023

As soon I recived my new boards, I began to build a simple prototype version of my computer with some RAM, ROM and I/O port to test some basic code. I used an Arduino Mega to debug the address and data line (based on rehsd design) :

After 3 weeks of debuging I was able to make some basic code that output value to the LED bargraph located on the right of the breadboard. Next step was to interface with something more complex, I had some VFD screens with a 8 bits parallel interface in my parts bin so I decided to gave it a shot.

I was able to output the classic 'Hello World' on the VFD screen. (The last letters are not seen due to the camera shutter)

Now that I'm able to write to the I/O port I decided to order more chips for more complex interactions :

• W65C22 - Western Digital - Versatile Interface Adapter (VIA)
• KS82C55A - Samsung - Programmable Peripheral Adapter (PPI)

When Ebay shoping for the VIA and PPI chips I stumble on a broken Tandon 80286 motherboard sold only for parts, so I decided to grab it and try to reverse engineer the board to gain some insight on its design.

To be continued ...

Dom