[vidarh]

It's pretty unusual to use double-buffering on the C64 - wastes memory. You'll find a lot of code times screen updates to the raster interrupt to either do updates during virtual blank, or start updates after the portion of the screen in question was updated. Of course that assumes you can do the updates in one frame, so you will find exceptions.

[cjauvin]

In fact, I don't know if what I did really corresponds to "real" double-buffering: at any point, the next move is created in an alternate buffer, which, when ready, is then switched as the visible portion of the video RAM (at vblank, using the raster interrupt). It works ok, but it's also quite possible that this mechanism might be a bit overkill.