Typically when we hear the term “System-on-Chip” bandied around, our mind jumps straight to modern ARM-based processors that drive smartphones and embedded devices around us. Coming a little bit more out of left field is [Jamie]’s 80186 core, that runs on Intel FPGAs.
[Jamie] has implemented the entire set of 80186 instructions in Verilog, and included some of the undocumented instructions too. This sort of attention to detail is important – real world parts don’t always meet the original specifications on paper, and programmers can come to rely on this. The key to compatibility is understanding how things perform in the real world, not just on the spec sheet.
Not content to simply simulate a CPU, all the necessary peripherals for a complete working system have been worked into the design as well. There’s RAM, a UART, as well as CGA graphics and a PS/2 controller that is necessary if you’d like to actually use any sort of human input device.
[Jamie] has released the code under a GPL licence, and it’s available at GitHub. It’s a good basis if you want to play around with what was once a commercial CPU at a logic level. The development guide is also available if you need to really drill down into the details. It’s a cool project, and makes a great contrast to [Jamie]’s previous work – the Oldland 32-bit core.