http://www.ascotti.org/programming/side/side.htm
The source code of the SIDE - Space Invaders Didactic Emulator
http://www.randelshofer.ch/fhw/gri/holzi.html
A four bit demo computer in Java (slightly buggy, as I discovered)
I might integrate this architecture though...
http://www.pastraiser.com/cpu/i8080/i8080_opcodes.html
OpCode Scheme for the Intel 8080 processor
http://www.spaceinvaders.de/
A german Space Invaders Homepage, with a flash version of the game
(GPL Copyleft) Martti Kühne, 20.8.2008