* Even logical VRAM addresses (logical address bit 0 = 0) map to VRAM0 and use R46 for masking.
* Odd logical VRAM address (logical address bit = 1) map to VRAM1 use R47 for masking.
=== Coordinates ===
* sx,sy,dx and dy use image space coordinates. Image space width can be 256, 512, 1024 or 2048 pixels. Image space coordinates are not the same as the display coordinates and display width and height. Coordinate masking is based on image space coordinates.
* the image space height is computed from the vram size, bits per pixel and image space width based on an equation like this:
image space width in bytes = (image size width * image bpp)/8
height = vram size bytes / image space width in bytes;
For a vram size of 512 this gives image space heights of &1000,&800,&400,&200,&100 and &80.
=== VRAM ===
