I remember a few years ago writing an emulator for an 8 bit processor, which IIRC, never really existed. It was thought up by someone in order to write a emulator, and was referenced a lot for beginners in the field of emulation. I lost the code that I had and I wanted to look it up again. (bummer really. It had a nice debugger, with register, stack, and memory views and break points. Full screen, sound, saved states. I liked it a lot D: )
I’ve been googling with no luck. The name in my head was Z80, but I quickly realized that that was the processor for the Gameboys xD hahaha
Chip-8 is what I was looking for!
I came across it here: http://www.zophar.net/chip8.html
Found out it wasn’t technically a made up processor, but actually a made up language created for the purpose of writing basic games in old computers. The reason I had it in my head for emulation is because, by writing an emulator for this, you get a very good idea of how to efficiently process op-codes in the emulation of something like a real processor. So it wasn’t so much of a “Here is a useful thing to emulate,” but more of a “This would be good to show you how to do design the emulator, then you can move on to more complicated things.”