VSP (Variable Screen Positioning), also known as HSP,
allows arbitrary x-placement of a bitmap, with the bitmap
wrapping around at the border.
It appears that it is possible to quickly shift the starting memory location of the buffer that contains the video memory, which means the rasteriser shifts everything around. This allows smooth horizontal/vertical scrolling - the program only needs to write the changed column/row instead of the entire screen.
C64 modding wikipedia page has more:
http://en.wikipedia.org/wiki/Commodore_64_demos
It appears that it is possible to quickly shift the starting memory location of the buffer that contains the video memory, which means the rasteriser shifts everything around. This allows smooth horizontal/vertical scrolling - the program only needs to write the changed column/row instead of the entire screen.http://www.lemon64.com/forum/viewtopic.php?t=42580&sid=c...