Freeing the DMA

There is a way to have a completely bitplane-DMA-free display. The demo 'Roots' is the one that uses it in rotator/distorter part with 3x3 pixel display. If you turn off sprite DMA while the sprite is shown, i.e. between sprite's start and stop boundaries, DMA stops updating sprite DAT registers, but sprite is kept shown. While sprite DMA is off, whole sprite is filled with SPRxDAT's contents. It's the only case, I'm aware of, when you can see anything on screen (i.e. fill whole screenwith a pattern), while the chipmem bus is completely free. =)

Interesting links: