I just thought of another intersting example. The version of adventure I used to play (550 point Geotz B01) behaved differently on a Z80 and a 8080. Something happened at the beginning of the game on a Z80 (It asked for your name, or have a version message, or something) which did not happen on an 8080/85. With that exception, it worked fine on either processor. That allways struck me as odd, and became my test for what processor was in a system. Les