After my version for the Atari 800XL, I now made also an Asteroids emulator for the Commodore 64. The original program of the Atari arcade machine, which is 6502 based, is directly executed by the C64's 6510 CPU. The graphics and sound hardware of the original machine is (more or less) exactly simulated by the C64 in software. The main challenge was (and a little bit still is) to accomplish an acceptable and constant speed.
If you are interested, you can visit my homepage for a description, screenshots, a video, and the download of the PRG file:
http://web.utanet.at/nkehrer/
Have fun!
Norbert