There are several projects tried to emulate a Commodore 64 as close to the original as possible. This includes emulating all undocumented features and quirks of

There are several projects tried to emulate a Commodore 64 as close to the original as possible. This includes emulating all undocumented features and quirks of the VIC-II chip that creates the video output. This is important since many great games and demos for the C64 made heavy use of these quirks. By using the die shot, you can reengineer all internal logic and find and understand those quirks fully.