 largely undocumented, tool for generating special
effects. It is used often by commercial games and demos alike.&nbsp; Its
most common use is to change one or more of the scroll registers mid-frame;
some games also change the video mode or palette mid-frame with it.&nbsp;
It is set up similar to DMA, except that $43?5 is ignored and probably,
bits 3, 4, 5 and 7 of $43?0 are ignored.

<P><B>Normal HDMA</B>

<P>There are two types of HDMA, controlled by bit 6 of register $43?0.&nbsp;
"Normal" HDMA is the sim