The background is the Mitsubishi has a nifty single-chip RISC computer that integrates RAM on the same chip as the CPU. But they didn't have any software for it. So they got a bright summer intern named Curtis Wickman to port Squeak to it.
Curtis had to write all the device drivers from scratch, including a display driver, the mouse and keyboard handlers, a Flash RAM file system, a loader, and sound output.
This took four to six weeks, I think. However, we were then able to put a generic Squeak image onto it and it looked and behaved exactly as it does on a PC or Macintosh. Even though we knew intellectually that this would be the case, it was somewhat mind-bending when Alan grabbed the mouse during our demo began doing an unrehearsed demo and everything worked perfectly!
The amount of code required for this "bare machine" implementation is quite modest; 2000 lines of C and a hundred or so of assembly code, as I recall. -- John Maloney