An eForth for Arduino UNO/Nano implemented in C..ino sketch file can be openned in Arduino IDE, no programmer to overwrite bootloader needed. Has 16-bit cells and stacks. Can read/write Arduino GPIO ...

[Damian Peckett] has implemented an Apple ][, its 6502 processor, and a cassette port, all on an Arduino Uno. If that wasn’t enough, he also uses a PS/2 keyboard for input and outputs analog VGA.

The 30-pin SIMM shown above is capable of storing up to (hold on to your chairs…) 16MB but due to limited amount of available IOs on the Atmega328p only 256KB can be used.