The Kim-Uno — a Kim-1 simulator

July 4, 2015 | Arduino, Emulation, My Projects, Retrocomputing | By: Mark VandeWettering

Ken Boak had mentioned on twitter that someone was creating a blinken-lights front end for the simh simulator of the PDP-8, called the PiDP-8, since you can power the entire thing from a Raspberry Pi. Very cool, but not quite available yet. What was available from Oscar is the Kim-Uno, a simulator for the old KIM-1 computer, a single board computer based upon the MOS6502 with a simple LED display and a whopping 1K of memory, first shipped in 1977 or so for about $245. The simulator is incredibly simple: a board, buttons, leds, and an Arduino Micro to drive it all. I went ahead and ordered one, just for kicks.

But you don’t actually need the hardware to play with this: you can get the code running on an ordinary Arduino Uno. So I did. It’s setup to run Microchess out of the box. Microchess is cool because it can play chess in less than 1K of code, and probably was the first commercial game software produced for hobbyist computers.

The Kim-Uno sketch is a little bit odd though. I’ve begun tinkering with it, and cleaning it up a bit. First of all, I thought it was confusing the way it tried to include the 6502 core emulation (written by Mike Chambers). It is written in C, and to merge it into the sketch required a bit of chicanery using ‘extern “C”‘ directives. Bleh, I renamed cpu.c to cpu.cpp, and cleaned that up. I fixed some forward declarations. I uncovered a couple of bugs by paying attention to compiler warnings. It won’t even come close to compiling on non-Arduino platforms, so I deleted lots of conditional definitions. And I generally just tidied things up. Along the way, I checked out the code that Oscar put in to scan the six digit display, which took a lot of pins. As is happens, I had an 8 digit display which used the 74HC595, which I had gotten working before using an interrupt driven display driver. I merged that code in, and now I had a hardware display like the Kim wired to my Uno. Probably refreshes more often than the original, but looks great!

When I get my code tidied up more, you’ll be able to download it on github. Stay tuned.